Placenta - Abnormalities

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Placental implantation abnormalities

The placenta is a mateno-fetal organ which begins developing at implantation of the blastocyst and is delivered with the fetus at birth. As the fetus relies on the placenta for not only nutrition, but many other developmentally essential functions, the correct development of the placenta is important to correct embryonic and fetal development.

Abnormalities can range from anatomical associated with degree or site of inplantation, structure (as with twinning), to placental function, placento-maternal effects (pre-eclampsia, fetal erythroblastosis) and finally mechanical abnormalities associated with the placental (umbilical) cord.

Morbidly adherent placenta (MAP) is the general clinical term used to describe the different forms of abnormal placental implantation (Accreta, Increta and Percreta). Clinical ultrasound indicators are the presence of an interruption of the bladder line, absence of a retroplacental clear zone, and the presence of placental lacunae.

A 2009 longitudinal Norwegian study suggests an association between large placenta relative to fetal size "disproportionately large placenta relative to birth weight was associated with increased risk of (adult) cardiovascular disease death."[1] See also the DOHAD hypothesis.

This current page lists some abnormalities associated with the placenta and also provides links to other resources. (See also Week 2 Abnormalities - Hydatidiform mole)

Placenta Links: placenta | Lecture - Placenta | Lecture Movie | Practical - Placenta | implantation | placental villi | trophoblast | maternal decidua | uterus | endocrine placenta | placental cord | placental membranes | placenta abnormalities | ectopic pregnancy | Stage 13 | Stage 22 | placenta histology | placenta vascular | blood vessel | cord stem cells | 2013 Meeting Presentation | Placenta Terms | Category:Placenta
Historic Embryology - Placenta 
1883 Embryonic Membranes | 1907 Development Atlas | 1909 | 1910 Textbook | 1917 Textbook | 1921 Textbook | 1921 Foetal Membranes |1921 human | 1921 Pig implantation | 1922 Single placental artery | 1923 Placenta Review | 1939 umbilical cord | 1943 human and monkey | 1944 chorionic villus and decidua parietalis | 1946 placenta ageing | 1960 monkey | 1972 Placental circulation | Historic Disclaimer

Some Recent Findings

  • Review - Defense and infection of the human placenta[2] "The placenta functions as a shield against infection of the fetus. The innate and adaptive immune defenses of the developing fetus are poorly equipped to fight infections. Infection by bacteria, viruses, and protozoa may cause infertility, spontaneous abortion, stillbirth, growth retardation, anomalies of development, premature delivery, neonatal morbidity, and mortality. However, appreciation of the human microbiome and host cell-microbe interactions must be taken into consideration as we try to determine what interactions are pathologic. Infection is typically recognized histologically by the presence of inflammation. Yet, several factors make comparison of the placenta to other human organs difficult. The placenta comprises tissues from two persons, complicating the role of the immune system."
  • Effect of site of placentation on pregnancy outcomes in patients with placenta previa[3] "This retrospective study included 678 cases of placenta previa. Basic information and pregnancy outcome data were collected. Differences between the different placenta previa positions and pregnancy outcomes were compared using the chi-square and independent t tests. Logistic and multiple regression analyses were used to calculate the odds ratios (ORs) to determine the risk factors for PAS disorders and postpartum hemorrhage and evaluate the effect of placental attachment site on pregnancy outcomes. RESULTS: There was no significant difference between the PAS disorders rate and the incidence of complete placenta previa depending on the type of placentation; however, placental attachment site influenced the pregnancy outcome. Placental attachment to the anterior wall was associated with shorter gestational age, low birth weight, lower Apgar score, higher prenatal bleeding rate, increased postpartum hemorrhage, longer duration of hospitalization, and higher blood transfusion and hysterectomy rates compared to cases with lateral/posterior wall placenta. Placental attachment at the incision site of a previous cesarean section significantly increased the incidence of complete placenta previa and PAS disorders compared with placental attachment at a site without incision, but did not significantly influence pregnancy outcomes. Placental attachment to the anterior wall was an independent risk factor for postpartum hemorrhage in patients with placenta previa. Placental attachment to a previous incision site was an independent risk factor for PAS disorders. CONCLUSION: The site of placental attachment in patients with placenta previa has an important influence on the pregnancy outcome. When the placenta is located on the anterior wall, clinicians should pay attention to the adverse pregnancy outcomes and the possibility of massive postpartum hemorrhage. In cases of placental attachment to the uterine incision site, physicians should be highly vigilant regarding the occurrence of PAS disorders."
  • Complete placenta previa ultrasound biometry and surgical outcomes[4] "To evaluate the relationship between surgical outcomes and ultrasound measurement of placental extension beyond the cervical os in women with placenta previa. ...In total, 157 women had placenta previa, ultrasound, and delivery data: 86 (55%) had a placental extension of <40 mm, and 71 (45%) had a placental extension of ≥40 mm. Women with placental extension of ≥40 mm had increased surgical time, blood loss > 2,000 mL, blood transfusion, and rate of peripartum hysterectomy. After multivariate analysis, only peripartum hysterectomy and surgical time > 90 minutes remained significant, p ≤ 0.05 and p ≤ 0.01, respectively. In women with placenta previa, the placental extension ultrasound measurement of ≥40 mm is a predictor of adverse surgical outcomes."
More recent papers  
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Search term: Placenta Abnormalities | Placenta Previa

Older papers  
These papers originally appeared in the Some Recent Findings table, but as that list grew in length have now been shuffled down to this collapsible table.

See also the Discussion Page for other references listed by year and References on this current page.

  • Hypoxic ischemic encephalopathy in newborns linked to placental and umbilical cord abnormalities[5] "Birth asphyxia and hypoxic ischemic encephalopathy (HIE) of the newborn remain serious complications. We present a study investigating if placental or umbilical cord abnormalities in newborns at term are associated with HIE. A prospective cohort study of the placenta and umbilical cord of infants treated with hypothermia (HT) due to hypoxic brain injury and follow-up at 12 months of age has been carried out. ...A velamentous or marginal umbilical cord insertion and histological abruption was associated with the risk of severe HIE. Velamentous or marginal umbilical cord insertion was found in 39% among HIE cases compared to 7% in controls." Neural System - Abnormalities
  • The branching pattern of villous capillaries and structural changes of placental terminal villi in type 1 diabetes mellitus[6] "In this paper, normal placental terminal villi and pathological villi of type 1 diabetic placentas were compared concerning the structure of villous stroma, spatial arrangement of villous capillary bed and quantitative assessment of capillary branching pattern. ...The quantitative assessment of capillary branching has shown that villous capillaries are more branched in diabetic placentas. It is concluded that type 1 maternal diabetes enhances the surface area of the capillary wall by elongation, enlargement of diameter and higher branching of villous capillaries and disrupts the stromal structure of terminal villi." maternal diabetes
  • Velamentous cord insertion caused by oblique implantation after in vitro fertilization and embryo transfer[7] "We present a case of a 36-year-old pregnant female after intracytoplasmic sperm injection. Ultrasonographic examination at 8 weeks' gestation revealed umbilical cord insertion with a viable fetus located on the septum membrane of dichorionic twin pregnancy near the anterior wall, while the other fetus was observed to have vanished. Next, this umbilical cord was seen to connect to the anterior wall and the placenta developed on the posterior wall later in the pregnancy. As a result, velamentous cord insertion with long membranous umbilical vessels developed at the time of delivery. The present case indicates that the assessment of the cord insertion site during the early gestation period is very important to predict any abnormality of the cord insertion site at the time of delivery. Furthermore, this case is valuable to understand the pathophysiological development of the placenta and velamentous cord insertion. "

Placenta Shape

Circumvallate placenta

Placentas are generally round or oval in shape and can also be "irregular" (multilobate, "star") shapes. These irregular shaped placentas have been associated with lower birth weight for placental weight suggesting an altered function.[8]

Embryo Virtual Slides

Human Circumvallate Placenta

Circumvallate placenta 01.jpg

 ‎‎Mobile | Desktop | Original

Placenta Abnormal | Embryo Slides
Circumvallate placenta is an abnormally shaped placenta where the chorionic membranes are not inserted at the edge of the placenta, but are located inward from the margins toward the placental cord. The membranes are described as "doubled back" over the fetal surface of the placenta.

Placenta Weight

A recent Canadian study of 87,600 singleton births[9] has identified a number of risk factors for both high and low placental weight. Some factors are associated either before, after or both accounting for birthweight.

Low placental weight

  • chronic hypertension (before and after accounting for birthweight).
  • pre-eclampsia (before, but not after adjustment for birthweight).

High placental weight

  • anaemia (before and after adjustment for birthweight).
  • gestational diabetes (before and after adjustment for birthweight).
  • smoking (after adjustment for birthweight).
  • Placental and cord determinants include chorioamnionitis, chorangioma/chorangiosis, circumvallate placenta and marginal cord insertion.

Placenta Accreta

MRI Placenta accreta showing uterine bulging into the bladder.[10]

The term placenta accreta refers to abnormal adherence, with absence of decidua basalis. The incidence of placenta accreta also significantly increases in women with previous cesarean section compared to those without a prior surgical delivery.[11][12] Detection bu ultrasound in the first trimester has low sensitivity (41%), that increases in the second trimester (60%) and third trimester (83,5%}.[13]

Placenta accreta 01.jpg

Ultrasound features:[14]

  1. Deficiency of retroplacental sonolucent zone
  2. Vascular lacunae
  3. Myometrial thinning
  4. Interruption of bladder line

Placenta Increta

Placenta Increta occurs when the placenta attaches deep into the uterine wall and penetrates into the uterine muscle, but does not penetrate the uterine serosa.

Placenta increta accounts for approximately 15-17% of all placenta abnormality cases.

Placenta previa and increta 02.jpg

Placenta Increta and Previa[15]

Placenta Percreta

In placenta percreta the placental villi penetrate the myometrium and through to uterine serosa.

MRI Surgery
Placenta percreta 04.jpg Placenta percreta 03.jpg
Placenta Percreta MRI[16] Surgical photograph
Showing the placenta extending through uterine wall (+) and covered by
thin serosal layer (arrow), no features of bladder invasion.

Placental villi penetrate myometrium and through to uterine serosa.

See clinical article on the laparoscopic management of placenta percreta. [17]

Placenta percreta 01.jpg

Placenta Percreta Histopathology[18]

Placenta Previa

historic model of Placenta Previa (praevia)

Historically, Paul Portal (1630-1703), a French physician[19], was the first to describe in 1685 a case of placenta previa in his "The Compleat Practice of Men and Women Midwives".

In this placental abnormality, the placenta overlies internal cervical os of uterus, essentially covering the birth canal. In the third trimester and at term, abnormal bleeding can require caesarian delivery and can also lead to abruptio placenta. This condition occurs in approximately 1 in 200 to 250 pregnancies and risk factors include prior cesarean delivery, pregnancy termination, intrauterine surgery, smoking, multifetal gestation, increasing parity, and maternal age. Ultrasound screening programs during 1st and early 2nd trimester pregnancies now include placental localization. Diagnosis can also be made by transvaginal ultrasound.

A retrospective study of from 59,149 women of 724 pregnancies (1.2%) diagnosed with a complete or partial previa, identified no associated with fetal growth restriction.[20]

A more recent retrospective study from 678 cases of placenta previa did not show differences depending on the type of placentation, but in the site of placentation.[3]

  • Anterior wall - associated with shorter gestational age, low birth weight, lower Apgar score, higher prenatal bleeding rate, increased postpartum hemorrhage, longer duration of hospitalization, and higher blood transfusion and hysterectomy rates compared to cases with lateral/posterior wall placenta.
  • Previous cesarean incision site - increased the incidence of complete placenta previa and PAS disorders compared with placental attachment at a site without incision, but did not significantly influence pregnancy outcomes.

Placenta previa does not appear to be affected by maternal age for maternal/neonatal outcomes.[21]

Placenta previa 01.jpg

Placenta previa MRI[16]

A 2007 Canadian study[22] identified that following first live birth delivery by caesarean section there is a 47% increased risk of placenta praevia and 40% increased risk of placental abruption in the second pregnancy with a singleton.

See also recent advances in the management of placenta previa. [23][12]

Ultrasound Placenta Previa

Placenta previa - anterior.jpg Placenta previa ultrasound 01.jpg
Anterior placenta position (upper arrow) in relation to cervix os (lower arrow). Posterior placenta position (arrow) in relation to cervix os (triangle).
Ultrasound placenta previa 01.jpg
US Placenta Previa GA33week icon.jpg
 ‎‎Placenta Previa
Page | Play

Ultrasound movie showing the fetal (GA 33 week) placenta.

Placental tissue is seen on the anterior and posterior uterine wall and completely covers the cervix.

Links: Ultrasound

Vasa Previa

Vasa previa (vasa praevia) placental abnormality where the fetal vessels lie within the membranes close too or crossing the inner cervical os (opening) and generally diagnosed (98%) by ultrasound. This occurs normally in 1:2500-5000 pregnancies and leads to complications similar too those for placenta previa.[12] Approximately 28% of prenatally diagnosis cases result in emergent preterm delivery.[24]

Type II is defined as the condition where the fetal vessels are found crossing over the internal os connecting either a bilobed placenta or a succenturiate lobe with the main placental mass.[25]

There are suggestions that colour doppler ultrasound can be used to visualise the blood vessels in high-risk cases and if required elective caesarean performed at 35–36 weeks in cases diagnosed as vasa praevia.[26]

Two main associations:

  1. velamentous insertions (25–62%)
  2. vessels crossing between lobes in succenturiate or bilobate placentas (33–75%)

Some recent evidence of successful in utero laser ablation of type II vasa previa at 22.5 weeks of gestation.

US Vasa Previa GA32week.jpg
 ‎‎Vasa Previa
Page | Play

Vasa previa ultrasound movie

Management of vasa previa

The following text is from a recent paper identifying the Canadian guidelines for the management of vasa previa.[27]

  1. If the placenta is found to be low lying at the routine second trimester ultrasound examination, further evaluation for placental cord insertion should be performed. (II-2B)
  2. Transvaginal ultrasound may be considered for all women at high risk for vasa previa, including those with low or velamentous insertion of the cord, bilobate or succenturiate placenta, or for those having vaginal bleeding, in order to evaluate the internal cervical os. (II-2B)
  3. If vasa previa is suspected, transvaginal ultrasound colour Doppler may be used to facilitate the diagnosis. Even with the use of transvaginal ultrasound colour Doppler, vasa previa may be missed. (II-2B)
  4. When vasa previa is diagnosed antenatally, an elective Caesarean section should be offered prior to the onset of labour. (II-1A)
  5. In cases of vasa previa, premature delivery is most likely; therefore, consideration should be given to administration of corticosteroids at 28 to 32 weeks to promote fetal lung maturation and to hospitalization at about 30 to 32 weeks. (II-2B)
  6. In a woman with an antenatal diagnosis of vasa previa, when there has been bleeding or premature rupture of membranes, the woman should be offered delivery in a birthing unit with continuous electronic fetal heart rate monitoring and, if time permits, a rapid biochemical test for fetal hemoglobin, to be done as soon as possible; if any of the above tests are abnormal, an urgent Caesarean section should be performed. (III-B
  7. Women admitted with diagnosed vasa previa should ideally be transferred for delivery in a tertiary facility where a pediatrician and blood for neonatal transfusion are immediately available in case aggressive resuscitation of the neonate is necessary. (II-3B)
  8. Women admitted to a tertiary care unit with a diagnosis of vasa previa should have this diagnosis clearly identified on the chart, and all health care providers should be made aware of the potential need for immediate delivery by Caesarean section if vaginal bleeding occurs. (III-B).

Abruptio Placenta

Represents interruption of the placenta by partial or complete separation, retroplacental blood clot formation and abnormal hemorrhage prior to delivery. There is significant perinatal mortality associated with abruptio placenta.[28]

Placenta Variants

Multilobed placenta succenturiata

Bilobed Placenta

Placenta with two equal-sized lobes connected by a thin bridge. No identified risks of this structure.

Bilobed placenta with velamentous cord insertion.jpg

Circumvallate placenta

Chorionic plate smaller than basal plate, edges rolled. Placental abruption and haemorrhage risks.

Placenta Membranacea

A rare placental abnormality where either all (diffuse placenta membranacea) or part (partial placenta membranacea) is covered by chorionic villi (placental cotyledons). Clinically the abnormality presents with vaginal bleeding, in the second or third trimester or during labor, due to an associated placenta previa.[29] Ultrasound has been used to detect this condition.[30]

Links: Search PubMed | Ultrasound

Succenturiate Placenta

Additional lobule separate from the main part of placenta. Risk of vessel rupture and placenta retention.

Links: Search PubMed | Ultrasound

Battledore Placenta

Placenta battledore (batyldoure = a beating instrument) is a term describing a placenta where the umbilical cord is attached at the margin. Occurs 7- 9% in singleton pregnancies and 24-33% in twin pregnancies and may effect placental function/fetal growth. The description probably comes from the similarity to a bat or paddle.

Links: Search PubMed | Ultrasound

Chronic Intervillositis

(massive chronicintervillositis, chronic histiocytic intervillositis) Rare placental abnormality and pathology defined by inflammatory placental lesions, mainly in the intervillous space (IVS), with a maternal infiltrate of mononuclear cells (monocytes, lymphocytes, histiocytes) and intervillous fibrinoid deposition.[31]

Links: Search PubMed | Ultrasound

Placental Mesenchymal Dysplasia

Due to a similar "grape-like" placental appearance, this rare disorder placental mesenchymal stem villous hyperplasia has been mistaken both clinically and macroscopically for a partial hydatidiform molar pregnancy. The disorder also has a high incidence of both intrauterine growth restriction (IUGR) and fetal death.[32] The placental abnormality may be detected, but difficult to diagnose, by ultrasound.[33]

Current research suggests that placental cells may be originated from a mixed population of androgenetic (paternal-derived genome only) and biparental cells.[34] This means that chorionic villus sampling can provide a differential diagnosis between this and a partial mole.[35]


This condition is also known as gestational proteinuric hypertension and occurs in occurs in approximately 2 to 4% of all pregnancies. The pathogenesis of eclamptic convulsions remains unknown and women with a history of eclampsia are at increased risk of eclampsia (1-2%) and preeclampsia (22-35%) in subsequent pregnancies. "Magnesium sulfate is the drug of choice for reducing the rate of eclampsia developing intrapartum and immediately postpartum."(see Sibai BM. 2005).

Recent research using a large population study in Norway has shown a strong generational association such that daughters of women who had pre-eclampsia during pregnancy had more than twice the risk of pre-eclampsia themselves. The paper concludes "Maternal genes and fetal genes from either the mother or father may trigger pre-eclampsia. The maternal association is stronger than the fetal association. The familial association predicts more severe pre-eclampsia."[36]

Diabetic Placenta

Maternal Type 1 diabetes can alter placental vascular development. Effects may be due to either maternal hyperglycaemia or fatal hyperinsulinaemia with high glucose and insulin shown in other systems to alter vascularity, increasing vascular endothelial growth factor (VEGF), nitric oxide (NO) and protein kinase C (PKC).[37][38]

Features of the placental vessels include:

  • Increased angiogenesis
  • altered junctional maturity and molecular occupancy
  • increased leakiness

The placental terminal villi also show vascularity changes including both hypovascularity and hypervascularity. A recent study of the normal and diabetic placenta,[6] shows the diabetic placenta terminal villi were:

  • hypovascular villi - had a smaller diameter and a wavy course
  • hypervascular villi - had numerous capillaries, reduced stroma and were large in diameter.

Specific changes included:

  • villous stroma - collagen envelope around capillaries looked thinner and the network of collagen fibers seemed less dense.
  • stromal cells - loss of desmin filaments.
  • villous capillaries - were more branched.

Links: Maternal Diabetes

Placental Chorioangioma

Chorioangiomas are the most common tumour of the placenta, occurring in approximately 1 % of all placentas and are generally benign vascular tumours (haemangiomas).

  • Small chorioangiomas are generally not clinically significant and usually found incidentally.
  • Large chorioangiomas have been associated with a range of fetal conditions (fetal anemia, thrombocytopenia, hydrops, hydramnios, intrauterine growth retardation) including prematurity and stillbirth.
Placental Chorioangioma Ultrasound
Placental chorioangioma ultrasound 01.jpg Placental chorioangioma ultrasound 02.jpg
Ultrasound scan placenta and chorioangioma Ultrasound blood flow in chorioangioma
Placental Chorioangioma
Placental chorioangioma 01.jpg Placental chorioangioma 02.jpg Placental chorioangioma 03.jpg

Example of a placental chorioangioma forming a yellowish, well-circumscribed firm mass (5 cm × 5 cm) connected by two vessels to the placenta. Histopathologic examination revealed a placental disc 15 cm × 17 cm × 13 cm, with a three-vessel umbilical cord that was attached peripherally and measured 9 cm × 1.5 cm. The weight of the placenta was 530 g. The tumor was confirmed to be a chorioangioma.[39]

Hydatidiform Mole

Hydatidiform Mole

Another type of abnormality is when only the conceptus trophoblast layers proliferates and not the embryoblast, no embryo develops, this is called a "hydatidiform mole" (HM), which is due to the continuing presence of the trophoblastic layer, this abnormal conceptus can also implant in the uterus. The trophoblast cells will secrete human chorionic gonadotropin (hCG), as in a normal pregnancy, and may appear maternally and by pregnancy test to be "normal". Prenatal diagnosis by ultrasound analysis demonstrates the absence of a embryo.

There are several forms of hydatidiform mole: partial mole, complete mole and persistent gestational trophoblastic tumor. Many of these tumours arise from a haploid sperm fertilizing an egg without a female pronucleus (the alternative form, an embryo without sperm contribution, is called parthenogenesis). The tumour has a "grape-like" placental appearance without enclosed embryo formation. Following a first molar pregnancy, there is approximately a 1% risk of a second molar pregnancy.

  • The incidence of hydatidiform mole varies between ethnic groups, and typically occurs in 1 in every 1500 pregnancies.
  • All hydatidiform mole cases are sporadic, except for extremely rare familial cases.
  • A maternal gene has been identified for recurrent hydatidiform mole (chromosome 19q13.3-13.4 in a 15.2 cM interval flanked by D19S924 and D19S890).[40]

Links: Hydatidiform Mole | Week 2 - Abnormalities

Mole Types

Complete mole - chromosomal genetic material from the ovum (egg) is lost, by an unknown process. Fertilization then occurs with one or two sperm and an androgenic (from the male only) conceptus (fertilized egg) is formed. With this conceptus the embryo (fetus, baby) does not develop at all but the placenta does grow but it is abnormal and forms lots of cysts and has no blood vessels. These cysts look like a cluster of grapes and that is why it is called a hydatidiform mole (grape like). A hydatidiform mole miscarries by about 16 to 18 weeks gestational age. Since the diagnosis can be made by ultrasound before that time, it is better for you to have an evacuation of the uterus (D & C) so that there is no undue bleeding and no infection. Human chorionic gonadotropin (hCG) will assist in making the diagnosis.

Partial mole - three sets of chromosomes instead of the usual two and this is called triploidy. With such a pregnancy the chromosomal (genetic) material from the ovum (egg) is retained and the egg is fertilized by one or two sperm. Since with partial mole there are maternal chromosomes there is a fetus but because of the three sets of chromosomes this fetus is always grossly abnormal and will not survive. (Text modified from: International Society for the Study of Trophoblastic Diseases,see also JRM Gestational Trophoblastic Disease)

Tumour Growth

Like any tumour, unless removed there is a risk of progression:

Stage I: Tumor confined to uterus (non-metastatic)
Stage II: Tumor involving pelvic organs and/or vagina
Stage III: Tumor involving lungs, with or without involving pelvic structures and/or vagina
Stage IV: Tumor involving distant organs

Placental Mesenchymal Dysplasia

Due to a similar "grape-like" placental appearance, this rare disorder has been mistaken both clinically and macroscopically for a partial hydatidiform molar pregnancy. This disorder also has a high incidence of intrauterine growth restriction (IUGR) and fetal death.

Twin Pregnancy Mole

Hydatidiform mole and co-existent healthy fetus is a very rare condition with only 30 cases documented in detail in the literature.[41]

Links: International Society for the Study of Trophoblastic Diseases | Sydney Gynaecological Oncology Group Gestational Trophoblastic Disease | The Journal of Reproductive Medicine Gestational Trophoblastic Disease (1998) | Dana-Farber Cancer Institute Gynecologic Oncology Program

Cord Abnormalities

Velamentous Cord Insertion[42]

Velamentous Cord Insertion

(velamentous insertion) Clinical term for describing a placental abnormality where the placental cord inserts into the chorion laeve (placental membranes) away from the edge of the placenta. The placental vessels can also diverge as they traverse between the amnion and chorion before reaching the placenta.The placental vessels are therefore unprotected by Wharton's jelly where they traverse the membranes before they come together into the umbilical cord. This can cause hemorrhage if the vessels are damaged when the membranes are ruptured prior to birth. The condition is more common in monozygotic twins (15%) and triplets.

Velamentous cord insertion, with a low uterine body implantation site, has also been shown to affect fetal heart rate.[43]

Bilobed placenta with velamentous cord insertion.jpg

A bilobed placenta with velamentous cord insertion.

Cord Vessel Number

Placental cord ultrasound 02.jpg
Cord with one artery and one vein

Persistent Right Umbilical Vein

A fairly rare anomaly, a study of 15,237 obstetric ultrasound examinations performed after 15 weeks' gestation identified only 33 cases of persistent right umbilical vein.[44] Some studies have identified associated fetal anomalies with this condition[45], including cardiac abnormalities.[46]

A recent human embryo study of persistent right umbilical vein[47] identified 2 specimens:

  1. a specimen with a degenerating right umbilical vein (UV) joined the thick left UV in a narrow peritoneal space between the liver and abdominal cavity
  2. another specimen with a degenerating left UV joined a thick right UV in the abdominal wall near the liver.

In both specimens, the umbilical vein drained into the normal, umbilical portion of the left liver.

Cord Knotting

Placental cord true knot
There are few abnormalities associated with umbilical cord development, other that abnormally short or long cords, which in most cases do not cause difficulties.

In some cases though, long cords can wrap around limbs or the fetus neck, which can then restrict blood flow or lead to tissue or nerve damage, and therefore effect develoment.

Cord knotting can also occur (1%) in most cases these knots have no effect, in some cases of severe knotting this can prevents the passage of placental blood.

Umbilical cord torsion

Placenta- umbilical cord torsion.jpg Rare umbilical cord torsion, even without knot formation can also affect placental blood flow, even leading to fetal demise.[48]

Cord Length

Furcate cord

Refers to the separation of placental vessels before their attachment into the placenta.[49]

Fetal Erythroblastosis

This disease is also called Haemolytic Disease of the Newborn, an immune problem from fetus Rh+ /maternal Rh-, leakage from fetus causes anti-Rh antibodies, which is then dangerous for a 2nd child.


Placental Infections

Listeria maternal-fetal barrier

Several infective agents may cross into the placenta from the maternal circulation, as well as enter the embry/fetal circulation. The variety of bacterial infections that can occur during pregnancy is as variable as the potential developmental effects, from virtually insignificant to a major developmental, abortive or fatal in outcome.

Placental Malaria

Malaria (plasmodium falciparum)

Pregnant women have an increased susceptibility to malaria infection. Malarial infection of the placenta by sequestration of the infected red blood cells leading to low birth weight and other effects. There are four types of malaria caused by the protozoan parasite Plasmodium falciparum (main), Plasmodium vivax, Plasmodium ovale, Plasmodium malariae). This condition is common in regions where malaria is endemic with women carrying their first pregnancy (primigravida).

Links: Abnormal Development - Malaria

Placental Herpesvirus

A recent paper has identified using an in vitro model that human herpesvirus 8 (HHV-8) can infect the placenta[50]

Cytomegalovirus Placentitis

Clinical term for the cytomegalovirus infection of the placenta.

A earlier histological study[51] identified fixed connective tissue cells predominantly infected cell type in placental tissue. In addition, endothelial cells, macrophages and in some cases trophoblast infection. While a more recent in vitro study[52] suggests that all villi cell types are likely to be infected.

Links: Cytomegalovirus | Abnormal Development - Viral Infection

Placental Membranes

There are few documented abnormalities associated with feral membranes (chorion, amnion). Ultrasound measurement of abnormal yolk sac size/shape in early embryonic development has been suggested as an indicator of early gestational loss. The most common literature described abnormalities are those associated with abnormal vasularization of the chorion.


ICD Code: O41.1 Infection of amniotic sac and membranes Amnionitis Chorioamnionitis Membranitis Placentitis

The best known environmental effect is infection of chorion and/or amnion referred to as chorioamnionitis.[53]

Chronic chorioamnionitis histology.jpg

Chronic Chorioamnionitis Histology[54]

  • Stage 1 ((a, b) inflammation showing infiltration of lymphocytes limited to the chorionic trophoblast layer (a). CD3 immunostaining demonstrates that the majority of these cells are T cells (b).
  • Stage 2 (c, d) inflammation is characterized by infiltration of lymphocytes into the chorioamniotic connective tissue layer ((Stain - Haematoxylin Eosin), c), which are largely CD3+ T cells (d).

Links: Bacterial Infection | Placental Membranes

Placental Pathology

The following pathology information from a clinical paper.[55]

Chronic Villitis

This condition can occur following placental infection leading to maternal inflammation of the villous stroma, often with associated intervillositis. The inflammation can lead to disruption of blood flow and necrotic cell death.

Massive Chronic Intervillositis

(MCI) The maternal blood-filled space is filled with CD68-positive histiocytes and an increase in fibrin, occuring more commonly in the first trimester.

Meconium Myonecrosis

The prolonged meconium exposure leads to toxic death of myocytes of placental vessels (umbilical cord or chorionic plate).


A fetal malignancy that leads to an enlarged placenta, with tumor cells in the fetal circulation and rarely in the chorionic villi.


(protein C or S deficiency, factor V Leiden, sickle cell disease, antiphospholipid antibody) This condition can generate an increased fibrin/fibrinoid deposition in the maternal or intervillous space, this can trap and kill villi.

International Classification of Diseases

XV Pregnancy Childbirth

O12 Gestational oedema and proteinuria without hypertension


  • O12.0 Gestational oedema
  • O12.1 Gestational proteinuria
  • O12.2 Gestational oedema with proteinuria

O13 Gestational hypertension without significant proteinuria


Incl.: Gestational hypertension NOS Mild pre-eclampsia

O14 Gestational hypertension with significant proteinuria

[pregnancy-induced] Excl.: superimposed pre-eclampsia (O11)

  • O14.0 Moderate pre-eclampsia
  • O14.1 Severe pre-eclampsia
  • O14.2 HELLP syndrome Combination of hemolysis, elevated liver enzymes and low platelet count
  • O14.9 Pre-eclampsia, unspecified

O15 Eclampsia

Incl.: convulsions following conditions in O10-O14 and O16 eclampsia with pregnancy-induced or pre-existing hypertension

  • O15.0 Eclampsia in pregnancy
  • O15.1 Eclampsia in labour
  • O15.2 Eclampsia in the puerperium
  • O15.9 Eclampsia, unspecified as to time period Eclampsia NOS

  • Abruptio placentae (641.2)
  • Placenta previa (641.0, 641.1)
  • Postpartum hemorrhage (666.0–666.2)


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Search PubMed

Search Pubmed: Placenta Abnormalities | Placenta Accreta | Placenta Increta | Placenta Percreta | Placenta Previa | Vasa Previa


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Simpson AR. (1879). Observations on Some Forms of Sterility and on Placenta Prævia in First Labours: With Illustrative Cases. Edinb Med J , 24, 769-782. PMID: 29640651

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Placenta Terms (expand to view) 
  • after-birth - term used to describe the delivery of placenta and placental membranes following birth of the child.
  • allantois - An extraembryonic membrane, endoderm in origin extension from the early hindgut, then cloaca into the connecting stalk of placental animals, connected to the superior end of developing bladder. In reptiles and birds, acts as a reservoir for wastes and mediates gas exchange. In mammals is associated/incorporated with connecting stalk/placental cord fetal-maternal interface.
  • amniocentesis - Clinical term for a prenatal diagnostic test where an ultrasound guided needle is used to extract a sample of the amniotic fluid. Amniocentesis
  • anastomosis - Term used to describe the connection between two tubes. Applied to describe the connection between peripheral blood vessels without an intervening capillary bed.
  • anchoring villi - (stem villi) describes the placental villi (embryonic) that attach to the decidua (maternal) tissue. The tip of the villi consists of a column of trophoblast cells attached to an epithelial plaque.
  • angioblasts form clusters or blood islands on surface of yolk sac.
  • angiogenesis - Term describing the development of new vessels from already existing vessels, this process is secondary to vasculogenesis which is the initial formation of first blood vessels by differentiation of pluripotent mesenchymal cells (extraembryonic mesoderm).
  • capsularis - portion of maternal decidua that covers the conceptus facing towards the uterine cavity.
  • cerebroplacental ratio - (CPR) a doppler ultrasound measurement calculated as the simple ratio between the middle cerebral artery pulsatility index (MCA‐PI) and the umbilical artery pulsatility index (UA‐PI). Fetuses with an abnormal ratio are thought to be a predictor of adverse pregnancy outcome.
  • chorioamnionitis - (CA) An intraamniotic puerperal infection described as having 3 forms: histologic, clinical (clinical chorioamnionitis, IAI), and subclinical. Intraamniotic infection is a common (2-4%) event in labor and the systemic inflammatory response can also lead to preterm birth and neonatal complications.
  • chorion - The extraembryonic membrane generated from trophoblast and extraembryonic mesoderm that forms placenta. chorion and amnion are made by the somatopleure. The chorion becomes incorporated into placental development. The avian and reptilian chorion lies beside the egg shell and allows gas exchange.
  • chorionic cavity - The fluid-filled extraembryonic coelom (cavity) formed initially from trophoblast and extraembryonic mesoderm that forms placenta. chorion and amnion are made by the somatopleure. The chorion becomes incorporated into placental development. The avian and reptilian chorion lies beside the egg shell and allows gas exchange. In humans, this cavity is lost during week 8 when the amniotic cavity expands and fuses with the chorion.
  • chorion frondosum - (frondosum = leafy) The chorion found on conceptus oriented towards maternal blood supply where the majority of villi form and proliferate, will contribute the fetal component of the future placenta.
  • chorion laeve - (laeve = smooth) The smooth chorion found on conceptus away from maternal blood supply (towards uterine epithelium and cavity) with very few villi present.
  • chorionic somatomammotropin - (CSH, human lactogen) A hormone synthesized within the placenta by syncytiotrophoblast cells. This protein hormone (190 amino acid) has a structure is similar to pituitary growth hormone.
  • chorionic villus sampling - (CVS) The taking a biopsy of the placenta, usually at the end of the second month of pregnancy, to test the fetus for genetic abnormalities.
  • coelocentesis - A sampling of extracoelomic fluid usually for an early prenatal diagnostic technique.
  • connecting stalk - the original extra-embryonic mesoderm structure attaching the embryonic disc to the chorion. The placental blood vessels form within this structure.
  • cord blood - (human umbilical cord blood, HUCB) A term used to describe blood collected from the placenta usually after birth. Has been identified as a source of stem cells with potential therapeutic uses and is stored in Cord Blood Banks throughout the world.
  • cord knotting Term describing umbilical or placental cord knotting. This occurs in about 1% prevents the passage of placental blood, pseudoknots also occur usually with no effect.
  • cord presentation - A term used to describe at birth the presence of the umbilical cord between the fetal presenting part and the cervix, with or without membrane rupture.
  • cord prolapse - A term used to describe at birth the descent of the umbilical cord through the cervix alongside (occult) or past (overt) the presenting part in the presence of ruptured membranes (incidence of 0.1% to 0.6%).
  • cotyledon - (Greek, kotyle = a deep cup) In the embryos of seed plants, the "seed leaves," in which nutrients are stored for use after germination. In placental animals, the term is also to describe the leaf-like structure of the placenta surface.
  • cytotrophoblast - The "cellular" trophoblast layer surrounding (forming a "shell") the early implanting conceptus. Beginning at uterine adplantation, proliferation and fusion of these cells is thought to form a second outer trophoblast layer, the syncytiotrophoblast. The cytotrophoblast layer contributes to formation of the placental villi, the functional component of the fetal placenta.
  • decidua basalis - The term given to the uterine endometrium at the site of implantation where signaling transforms the uterine stromal cells (fibroblast-like) into decidual cells. This forms the maternal component of the placenta, the decidualization process gradually spreads through the remainder of the uterus, forming the decidua parietalis.
  • decidua basalis reaction - Term describing the maternal endometrial changes that occur initially at the site of, and following, blastocyst implantation. Seen as a deposition of glycogen, fibrin and proliferation of blood vessels. See also decidualization.
  • decidua capsularis - The term given to the uterine endometrium which has been converted to decidua surrounding the conceptus on the smooth chorion side.
  • decidua parietalis - The term given to the remainder of the uterine endometrium, away from the site of implantation, that gradually becomes comverted to decidua.
  • decidual cell - The uterine stromal cells (fibroblast-like) that differentiate in response to both steroid hormones (progesterone) and embryonic signals. These cells then alter uterine environment to support further embryonic development as well as producing cytokines related to prolactin (PRL) and have an innate immune function.
  • decidual reaction - maternal endometrial reaction invoked in order to block the rapid extension of the implanting syncytium.
  • decidualization - (decidualisation, decidual reaction) The process by which uterine stromal cells differentiate in response to both steroid hormones and embryonic signals into large epitheliod decidual cells. This process is essential for the progress of implantation and establishing fetal-maternal communication.
  • DHEA - (dehydroepiandrosterone, androstenolone) precursor of sex steroid hormones and is converted to testosterone and estradiol. Postnatally, an abundant circulating steroid produced in the adrenal gland. The fetal adrenal cortex produces dehydroepiandrosterone sulfate (DHEA-S) used by the placenta to produce estrogens. DHEA, androstenedione, and testosterone can be metabolized to epiandrosterone, and etiocholanolone. PMID 15635500
  • fetal drug addiction - occurs when drugs used maternally cross the placental barrier and can establish neural/physiological addiction in the unborn fetus. drugs
  • fetal erythroblastosis - (Haemolytic Disease of the Newborn) A clinical term describing an immune response between fetal and maternal blood groups; from fetus Rh+ / maternal Rh-. The leakage of blood from fetus, particularly at birth, causes maternal anti-Rh antibodies, which is then dangerous for a 2nd or future pregnancies.
  • fetal intra-abdominal umbilical vein varix - (FIUV, umbilical vein varix) focal dilatation of the umbilical venous diameter at the level of cord insertion, the dilatation diameter increases linearly with gestational age. Represent about 4% of umbilical cord abnormalities

with an incidence of about 2.8 per 1,000 pregnancies, there is also a rarer form of extra-abdominal varices.PMID 24883288

  • fibrinoid layer - (Nitabuch's layer) A layer formed at maternal/fetal interface during placentation and is thought to act to prevent excessively deep conceptus implantation. Fibrin-type fibrinoid (maternal blood-clot product) and matrix-type fibrinoid (secreted by invasive extravillous trophoblast cells).
  • floating chorionic villi - Term used to describe the placental microanatomy structure of chorionic villi that are not attached to the maternal decidua and float in the maternal blood-filled space (lacunae). Structurally the same as anchoring chorionic villi conceptus side that are attached to the maternal decidua.These villi go through the same stages of development: primary villi - secondary villi - tertiary villi
  • hemotrophic nutrition - Term used to describe in late placenta development the transfer of blood-borne nutrition from maternal to embryo/fetuscompared to early histiotrophic nutrition.
  • heterotopic pregnancy - (Greek, heteros = other) Clinical term for a very rare pregnancy of two or more embryos, consisting of both a uterine cavity embryo implantation and an ectopic implantation.
  • histiotrophic nutrition - Term used to describe in early placenta development the intital transfer of nutrition from maternal to embryo (histiotrophic nutrition) compared to later blood-borne nutrition (hemotrophic nutrition). Histotroph is the nutritional material accumulated in spaces between the maternal and fetal tissues, derived from the maternal endometrium and the uterine glands. This nutritional material is absorbed by phagocytosis initially by blastocyst trophectoderm and then by trophoblast of the placenta. in later placental development nutrition is by the exchange of blood-borne materials between the maternal and fetal circulations, hemotrophic nutrition.
  • Hofbauer cells - Cells found within placental villi connective tissue. Have a role as macrophages of mesenchymal origin with potentially additional functions (remodeling, vasculogenesis, regulation of stromal water content).
  • Human chorionic corticotropin - (hCACTH) placental derived hormone equivilant to corticotropin (ACTH) from the pituitary.
  • Human chorionic gonadotrophin - (hCG) like leutenizing hormone, supports corpus luteum, originally secreted by trophoblast cells.
  • Human chorionic somatommotropin - (hCS, placental lactogen) hormone level increases in maternal blood through pregnancy, decreases maternal insulin sensitivity (raising maternal blood glucose levels and decreasing maternal glucose utilization) aiding fetal nutrition.
  • Template:Hydatiform mole - A uterine tumour with "grape-like" placenta appearance without enclosed embryo formation, arises mainly from a haploid sperm fertilizing an egg without a female pronucleus. It is one form of gestational trophoblastic disease(GTD), a number of abnormalities including hydatiform mole, invasive mole, choriocarcinoma and placental site trophoblastic tumor (PSTT).
  • hysterectomy – clinical term for the surgical removal of the uterus.
  • Langhans layer - cytotrophoblast cell layer.
  • maternal antibodies - antibodies from the mother's immune system that are capable of crossing placental barrier. They can provide immune protection to the embryo, but may also participate in immune disease (fetal erythroblastosis).
  • maternal sinusoids - placental spaces around chorionic villi that are filled with maternal blood. This is the closest maternal/fetal exchange site.
  • Nitabuch's layer - (fibrinoid layer) The layer formed at maternal/fetal interface during placentation and is thought to act to prevent excessively deep conceptus implantation. Fibrin-type fibrinoid (maternal blood-clot product) and matrix-type fibrinoid (secreted by invasive extravillous trophoblast cells).
  • Morbidly adherent placenta (MAP) A general clinical term used to describe the different forms of abnormal placental implantation (Accreta, Increta and Percreta).
  • oligohydramnios - Clinical term for the accumulation a deficiency of amniotic fluid during pregnancy. See also polyhydramnios, an excess of amniotic fluid.
  • persistent right umbilical vein - (PRUV) A placental cord abnormality associated with fetal abnormalities and poor neonatal prognosis. The estimated incidence of persistent right umbilical vein in a low-risk population is 1 : 526. PMID 12047534
  • polyhydramnios - Clinical term for the accumulation of excess amniotic fluid during pregnancy. See also oligohydramnios, a deficiency of amniotic fluid.
  • placenta - (Greek, plakuos = flat cake) The developmental organ formed from maternal and fetal contributions in animals with placental development. In human, the placenta at term is a discoid shape "flat cake" shape; 20 cm diameter, 3 cm thick and weighs 500-600 gm. Placenta are classified by the number of layers between maternal and fetal blood (Haemochorial, Endotheliochorial and Epitheliochorial) and shape (Discoid, Zonary, Cotyledenary and Diffuse). The placenta has many different functions including metabolism, transport and endocrine.
  • placenta accreta - The abnormal placental adherence, either in whole or in part of the placenta with absence of decidua basalis, leading to retention as an after-birth to the underlying uterine wall. The incidence of placenta accreta also significantly increases in women with previous cesarean section compared to those without a prior surgical delivery.
  • placental arteries - (umbilical arteries) In placental animals, the blood vessels which develop within the placental cord carrying relatively deoxygenated blood from the embryo/fetus to the placenta. In humans, there are two placental arteries continuous with the paired internal iliac arteries (hypogastric arteries) arising off the dorsal aortas. At birth this vessel regresses and form the remnant medial umbilical ligament.
  • placental cord - (umbilical cord) The placental cord is the structure connecting the embryo/fetus to the placenta. It is initially extra-embryonic mesoderm forming the connecting stalk within which the placental blood vessels (arteries and veins) form. In human placental cords the placental blood vessels are initially paired, later in development only a single placental vein remains with a pair of placental arteries. This structure also contains the allantois, an extension from the hindgut cloaca then urogenital sinus. Blood collected from the placental cord following delivery is a source of cord blood stem cells.)
  • placental diameter - is measured in the transverse section by calculating the maximum dimensions of the chorionic surface.
  • placental growth factor - (PlGF) A growth factor of the vascular endothelial growth factor (VEGF) family, released from the placental trophoblast cells and other sources that stimulates blood vessel growth.
  • placental malaria - The malarial infection of the placenta by sequestration of the infected red blood cells. This condition can be common in regions where malaria is endemic with women carrying their first pregnancy (primigravida).
  • placenta membranacea - rare placental abnormality characterized by the presence of chorionic villi directly attached to and covering the fetal membranes. Placenta Membranacea
  • placenta previa - placenta overlies internal os of uterus, abnormal bleeding, may require cesarian delivery.
  • placental thickness - is measured at its mid-portion from the chorionic plate to the basilar plate, on a longitudinal plane (less than 4 cm at term). Excludes any abnormalities (fibroids, myometrial contractions, or venous lakes). The placental thickness approximates in millimeters to the weeks of gestation.
  • placental vein - (umbilical vein) In placental animals, the blood vessels which develop within the placental cord carrying relatively oxygenated blood from the placenta to the embryo/fetus. In humans, there are initially two placental veins which fuse to form a single vein. The resence of paired veins in the placental cord can be indicative of developmental abnormalities.
  • placentophagia - Term used to descrbe the maternal ingestion of afterbirth materials (placental membranes and amniotic fluid) that can occur following mammalian parturition (birth).
  • primary villi - (primary chorionic villi) Term describing the earliest stage of embryonic placenta development. In humans, the conceptus during week 2 this first stage of chorionic villi development consists of only the trophoblastic shell cells (syncitiotrophoblasts and cytotrophoblasts) forming finger-like extensions into maternal decidua. Initially these finger-like projections cover the entire surface of chorionic sac and later become restricted to the placental surface. The villi stages are ongoing as the placenta continues to grow through both the embryonic and fetal development.
  • pre-eclampsia - During pregnancy a combination of high blood pressure, protein in urine and fluid retention resulting in maternal sudden excessive swelling of the face, hands and feet. Eclampsia is the subsequent development of convulsions, kidney failure, liver failure, clotting problems or mortality.
  • Rh alloimmunization - feto-maternal haemorrhage generally in late pregnancy results in an Rh-negative woman becoming sensitised to Rh-positive fetal cells that enter her circulation. Clinically treated with anti-D immune globulin prophylaxis, alloimmunization occurs in 9–10% of at-risk pregnancies. immune
  • secondary villi - (secondary chorionic villi) Term describing the second stage of embryonic placenta development. In humans, the conceptus during week 3 onward this stage of chorionic villi development consists of the trophoblastic shell cells (syncytiotrophoblast and cytotrophoblasts) filled with extraembryonic mesoderm forming finger-like extensions into maternal decidua. Initially these finger-like projections cover the entire surface of chorionic sac and later become restricted to the placental surface. The villi stages are ongoing as the placenta continues to grow through both the embryonic and fetal development. Placental villi stages: primary villi - secondary villi - tertiary villi
  • syncytiotrophoblast - A multinucleated cell currently thought to form by the fusion of another trophoblast cell the cytotrophoblasts, within the trophoblast layer (shell) of the implanting conceptus. In early development, these cells mediate implantation of the conceptus into the uterine wall and secrete the hormone (Template:Human Chorionic Gonadotrophin, hCG) responsible for feedback maintainance of the corpus luteum (in maternal ovary) and therefore maintaining early pregnancy.
  • trophoblast - (trophectoderm, Greek, trophe = "nutrition" and blast = a primordial cell) cells that firstly support adplantation, implantation and endocrine support of pregnancy. Contribute to the extraembryonic tissues, fetal placenta and membranes. Initially form 2 populations individual cytotrophoblast cells and their fused multinucleate syncytiotrophoblast cells.
  • Twin-twin transfusion syndrome - (TTTS) in monozygotic twins with monochorionic and diamniotic placenta, with intrauterine blood transfusion from one twin (donor) to another twin (recipient) where there is an imbalance of blood flow from the donor twin to the recipient twin. Clinically diagnosed by the alternate presence of polyhydramnios in one fetus and oligohydramnios in the co-twin, occurs in about 10% of monochorionic twins.
  • umbilical cord (placental cord) fetal attachment cord 1-2 cm diameter, 30-90cm long, covered with amniotic attached to chorionic plate, umbilical vessels (artery, vein) branch into chorionic vessels. Vessels anastomose within the placenta.
  • umbilical vein varix - (fetal intra-abdominal umbilical vein varix, FIUV) focal dilatation of the umbilical venous diameter at the level of cord insertion, the dilatation diameter increases linearly with gestational age. Represent about 4% of umbilical cord abnormalities

with an incidence of about 2.8 per 1,000 pregnancies, there is also a rarer form of extra-abdominal varices. PMID 24883288

  • vasculogenesis - formation of first blood vessels by differentiation of pluripotent mesenchymal cells (extraembryonic mesoderm) followed by angiogenesis which is the development of new vessels from already existing vessels.
  • vasculosyncytial membranes - localised areas of the placental villous membrane where the barrier thickness separating maternal and fetal circulations is reduced to as little as 1-2 microns. PMID 1287078
  • villi - Plural of villus, which is a thin projection from a surface. The term in development is used to describe the individual functional units together of the fetal placenta.
  • virus - small infectious agents that may cross the placental barrier. Can infect embryo and/or placenta and cause developmental abnormalities. (e.g. cytomegalovirus, rubella, measles).
  • Wharton's jelly - placental cord (umbilical cord) gelatinous connective tissue composed of myofibroblast-like stromal cells, collagen fibers, and proteoglycans. Increases in volume (myxomatous, connective tissue embedded in mucus) at parturition (birth) to assist closure of placental blood vessels. Matrix cells from Wharton's jelly have recently been identified as a potential source of mesenchymal stem cells (MSC), also called mesenchymal stromal cell. This placental cord substance is named after Thomas Wharton (1614-1673) an English physician and anatomist who first described this placental tissue.
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Cite this page: Hill, M.A. (2019, October 18) Embryology Placenta - Abnormalities. Retrieved from

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© Dr Mark Hill 2019, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G