The placenta abnormalities in which, a thin fibrous ring is present at the margin of the chorionic plate where the fetal vessels appear to terminate is:-
A. Circumvallate placenta
B. Placenta membranacea
C. Placenta marginata
D. Placenta Spuria
Correct Answer: C. Placenta marginata
Explanation
The placental abnormality described is Circumvallate placenta.
Explanation:
- In circumvallate placenta, the chorionic plate is smaller than the basal plate.
- Because of this, the membranes (amnion and chorion) fold back on themselves at the placental margin.
- This folding forms a thin, raised fibrous ring at the margin of the chorionic plate.
- The fetal blood vessels appear to end (terminate) at this ring instead of reaching the true placental edge.
Key features to remember:
- Presence of a thickened or fibrous ring at placental margin
- Fetal vessels stop at the ring
- Classified as an extrachorial placenta
- May be associated with complications like bleeding, preterm labor, or placental abruption
✅ Correct answer: Circumvallate placenta
Other Options Details
Here is a clear description of each option related to abnormal placental morphology:
A. Circumvallate Placenta
- It is an extrachorial placenta.
- The chorionic plate is smaller than the basal plate.
- A thick, raised ring is formed at the placental margin due to folding of membranes (amnion and chorion) toward the fetal side.
- Fetal blood vessels terminate at the ring and do not reach the edge.
- Clinical significance: Associated with antepartum hemorrhage, preterm labor, placental abruption, and fetal growth restriction.
B. Placenta Membranacea
- A rare condition where placental tissue spreads over most or all of the uterine cavity.
- The placenta develops as a thin membranous sheet instead of a single disc.
- Results from failure of placental villi to regress in areas other than the implantation site.
- Clinical significance: Can cause placenta previa and severe postpartum hemorrhage.
C. Placenta Marginata
- A milder form of extrachorial placenta.
- The chorionic plate is slightly smaller than the basal plate.
- Instead of a thick ring, there is a flat, thin membranous rim at the placental margin.
- Clinical significance: Usually less severe and often clinically insignificant compared to circumvallate placenta.
D. Placenta Spuria
- Refers to an accessory placental lobe without vascular connection to the main placenta.
- Differs from a succenturiate placenta, where accessory lobes have vascular connections.
- Formed due to localized persistence of chorionic villi.
- Clinical significance: Risk of retained placental tissue and postpartum hemorrhage.
Summary Table
Condition Key Feature Circumvallate placenta Thick raised ring at margin Placenta membranacea Placenta covers entire uterine cavity Placenta marginata Thin flat membranous rim Placenta spuria Accessory lobe without vessels
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Writer: Vandita Singh, Lucknow (GS India Nursing Group