BGDA Practical Placenta - Abnormalities

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Practical 14: Implantation and Early Placentation | Villi Development | Maternal Decidua | Cord Development | Placental Functions | Diagnostic Techniques | Abnormalities

Ectopic Implantation

Commences early stages of placentation.

  • Usually identified by ultrasound.
  • Presence of trophoblast cells in tube used to pathologically identify implantation.
Tubal Ectopic Bicornuate Uterus Ectopic
Ectopic 01.jpg
 ‎‎Ectopic Pregnancy
Page | Play
Bicornuate uterus ectopic movie icon.jpg
 ‎‎Bicornuate Ectopic
Page | Play
Ectopic 01.jpg Ectopic 01 zoom.jpg
Ectopic 01 limbs.jpg Ectopic 01 heart.jpg

USA Statistics
Ectopic Pregnancies- United-States 1970-1992.jpg

Ectopic Pregnancies- United-States 1970-1992[1]

Ectopic Pregnancies- United-States 1997-2006.jpg

Ectopic Pregnancies- United-States 1997-2006

Links: Ectopic Implantation | Ultrasound

Hydatidiform Mole

Hydatidiform Mole
MRI Complete 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.

  • Complete Mole - Only paternal chromosomes, chromosomal genetic material from the ovum (egg) is lost, by an unknown process.
  • Partial Mole - Ultrasound of partial mole confirmed by triploidy, chromosomal (genetic) material from the ovum (egg) is retained and the egg is fertilized by one or two sperm.

On ultrasound 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.

Links: Hydatidiform Mole | Week 2 - Abnormalities

Implantation Abnormalities

Morbidly adherent placenta (MAP) is the general clinical term used to describe the different forms of abnormal placental implantation (Accreta, Increta and Percreta).

Placenta abnormalities.jpg

Placenta previa and increta 02.jpg

Placenta previa and increta

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.

Multilobed placenta succenturiata
  • Placenta Accreta - 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.
  • 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 cases.
  • Placenta Percreta - placental villi penetrate myometrium and through to uterine serosa.
  • Placenta Previa - In this placenatal abnormality, the placenta overlies internal os of uterus, essentially covering the birth canal. This condition occurs in approximately 1 in 200 to 250 pregnancies. In the third trimester and at term, abnormal bleeding can require cesarian delivery and can also lead to Abruptio Placenta. Ultrasound screening programs during 1st and early 2nd trimester pregnancies now include placental localization. Diagnosis can also be made by transvaginal ultrasound.
  • Vasa Previa - (vasa praevia) placental abnormality where the fetal vessels lie within the membranes close too or crossing the inner cervical os (opening). Two main associations; 1. velamentous insertions (25–62%) and 2. vessels crossing between lobes in succenturiate or bilobate placentas (33–75%)
  • Multilobed Placenta Succenturiata - an accessory portion attached to the main placenta by an artery or vein.
  • Abruptio Placenta - a retroplacental blood clot formation, abnormal haemorrhage prior to delivery.
  • 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.

Cord Abnormalities

Velamentous Cord Insertion of the Placenta

Placenta velamentous cord 02.jpg

The placental cord inserts into the chorion laeve (placental membranes) away from the edge of the placenta.[2]

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 also be associated with vasa previa (see above) or haemorrhage caused if the vessels are damaged when the membranes are ruptured prior to birth. The condition is more common in monozygotic twins (15%) and triplets.

Cord Length

Excessively short or long cords (see additional information on cord page). Abnormally long cords may wrap around either extremities or neck of the fetus.

Cord Vessel Number

Placental cord ultrasound 02.jpg

Cord with only 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.[3] Some studies have identified associated fetal anomalies with this condition[4], including cardiac abnormalities.[5]

Cord Knotting

Placental cord true knot

Cord knotting can 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

Rare umbilical cord torsion, even without knot formation can also affect placental blood flow, even leading to fetal demise.

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.

Cytomegalovirus Placentitis

Clinical term for the cytomegalovirus infection of the placenta. Cytomegalovirus (CMV) is the most common congenital viral infection, causing sensory (hearing, visual) and psychomotor impairment.

A earlier histological study[6] 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[7] suggests that all villi cell types are likely to be infected.

Links: Cytomegalovirus | Abnormal Development - Viral Infection

Placental Herpesvirus

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

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

Practical 14: Implantation and Early Placentation | Villi Development | Maternal Decidua | Cord Development | Placental Functions | Diagnostic Techniques | Abnormalities

Additional Information

Additional Information - Content shown under this heading is not part of the material covered in this class. It is provided for those students who would like to know about some concepts or current research in topics related to the current class page.

Bilobed Placenta with Velamentous Cord Insertion

Bilobed placenta with velamentous cord insertion.jpg

Placenta - Abnormalities

Placenta Examination

Royal Hospital for Women

<pubmed>9518951</pubmed>| Am Fam Physician.

"A one-minute examination of the placenta performed in the delivery room provides information that may be important to the care of both mother and infant. The findings of this assessment should be documented in the delivery records. During the examination, the size, shape, consistency and completeness of the placenta should be determined, and the presence of accessory lobes, placental infarcts, hemorrhage, tumors and nodules should be noted. The umbilical cord should be assessed for length, insertion, number of vessels, thromboses, knots and the presence of Wharton's jelly. The color, luster and odor of the fetal membranes should be evaluated, and the membranes should be examined for the presence of large (velamentous) vessels. Tissue may be retained because of abnormal lobation of the placenta or because of placenta accreta, placenta increta or placenta percreta. Numerous common and uncommon findings of the placenta, umbilical cord and membranes are associated with abnormal fetal development and perinatal morbidity. The placenta should be submitted for pathologic evaluation if an abnormality is detected or certain indications are present."

Gestational hypertension-preeclampsia

  • also known as gestational proteinuric hypertension
  • a common pregnancy complication, with an incidence ranging from 2–8%.
  • lack of blood flow from the uterus to the placenta is always observed.
  • 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.

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."


Multiple Pregnancy

Monochorionic twin pregnancies Monochorionic triamniotic triplet pregnancy placenta
Monochorionic twin placenta 01.jpg Triplet placenta.jpg

Placental Weight

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."[9] See also the DOHAD hypothesis.

Other Online Resources

2013 Meeting Presentation- Placenta Circulation

Template:Placenta Terms

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 first trimester placenta | 1960 monkey | 1972 Placental circulation | Historic Disclaimer

  1. <pubmed>7823895</pubmed>
  2. <pubmed>23243528 </pubmed>| PMC3517836 | Case Rep Obstet Gynecol.
  3. <pubmed>7970470</pubmed>
  4. <pubmed>20922781</pubmed>
  5. <pubmed>26635256</pubmed>
  6. <pubmed>8236822</pubmed>
  7. <pubmed>21392403</pubmed>
  8. <pubmed>19115001</pubmed>
  9. <pubmed>19638481</pubmed>


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Cite this page: Hill, M.A. (2021, April 20) Embryology BGDA Practical Placenta - Abnormalities. Retrieved from

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© Dr Mark Hill 2021, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G