BGDA Practical Placenta - Abnormalities

From Embryology
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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
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Bicornuate uterus ectopic movie icon.jpg
 ‎‎Bicornuate Ectopic
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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

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.


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


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


J F Yetter Examination of the placenta. Am Fam Physician: 1998, 57(5);1045-54 PubMed 9518951

| 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."

Rolv Skjaerven, Lars J Vatten, Allen J Wilcox, Thorbjørn Rønning, Lorentz M Irgens, Rolv Terje Lie Recurrence of pre-eclampsia across generations: exploring fetal and maternal genetic components in a population based cohort. BMJ: 2005, 331(7521);877 PubMed 16169871


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."[6] See also the DOHAD hypothesis.

Other Online Resources

2013 Meeting Presentation- Placenta Circulation



Placenta Links: Introduction | Lecture - Placenta | Practical - Placenta | Implantation | Villi Development | Trophoblast | Maternal Decidua | Endocrine | Cord | Membranes | Abnormalities | Stage 13 | Stage 22 | Histology | Vascular Beds | Blood Vessel Development | Stem Cells | Category:Placenta


  1. Centers for Disease Control and Prevention (CDC) Ectopic pregnancy--United States, 1990-1992. MMWR Morb. Mortal. Wkly. Rep.: 1995, 44(3);46-8 PubMed 7823895
  2. Juliana Rocha, Joana Carvalho, Fernanda Costa, Isabel Meireles, Olímpia do Carmo Velamentous cord insertion in a singleton pregnancy: an obscure cause of emergency cesarean-a case report. Case Rep Obstet Gynecol: 2012, 2012;308206 PubMed 23243528 | PMC3517836 | Case Rep Obstet Gynecol.
  3. L M Hill, A Mills, C Peterson, D Boyles Persistent right umbilical vein: sonographic detection and subsequent neonatal outcome. Obstet Gynecol: 1994, 84(6);923-5 PubMed 7970470
  4. J Weichert, D Hartge, U Germer, R Axt-Fliedner, U Gembruch Persistent right umbilical vein: a prenatal condition worth mentioning? Ultrasound Obstet Gynecol: 2011, 37(5);543-8 PubMed 20922781
  5. Brianna Lide, William Lindsley, Margaret J Foster, Richard Hale, Sina Haeri Intrahepatic Persistent Right Umbilical Vein and Associated Outcomes: A Systematic Review of the Literature. J Ultrasound Med: 2015; PubMed 26635256
  6. Kari R Risnes, Pål R Romundstad, Tom I L Nilsen, Anne Eskild, Lars J Vatten Placental weight relative to birth weight and long-term cardiovascular mortality: findings from a cohort of 31,307 men and women. Am. J. Epidemiol.: 2009, 170(5);622-31 PubMed 19638481



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Cite this page: Hill, M.A. (2016) Embryology BGDA Practical Placenta - Abnormalities. Retrieved September 30, 2016, from https://embryology.med.unsw.edu.au/embryology/index.php/BGDA_Practical_Placenta_-_Abnormalities

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© Dr Mark Hill 2016, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G