In other cases, patients diagnosed with circumvallate placenta are able to carry their babies until term or near-term. Epidemiology
Circumvallate placenta is a very rare condition affecting pregnant women. This condition is a placental morphological abnormality, with the placenta being formed during the early periods of pregnancy. Women are able to become pregnant with the onset of ovulation and menstruation in early adolescence, with most women becoming pregnant during adulthood. Circumvallate placenta is currently known to affect about 1-2% of pregnancies. It is not virally transmissible to other individuals, nor can it be transferred through contact or respiration.There are no specific racial or ethnic groups that are more predisposed to acquiring a circumvallate placenta during pregnancy, however, as with all pregnancies, there are general risks factors that can put a pregnant woman at risk for complications, including circumvallate placenta. Notably, certain pregnancy complications, such as preeclampsia, tend to be almost three times as fatal in African American women compared to non-Hispanic white women, even though both groups tend to experience preeclampsia at almost the same rates. This is partially thought to be due to inequalities in accessing quality prenatal care in lower socioeconomic neighborhoods and the effect of structural racism within healthcare systems. Any woman residing in an area with a lower socioeconomic status, regardless of race or age, is predisposed to developing pregnancy complications like circumvallate placenta if quality prenatal care is not available.
Fetal blood vessels subdivide from the umbilical cord and spread diagonally throughout the parenchyma towards the edge of the placental plate.In a circumvallate placenta, the membranes often become restrained due to marginal infarct, hemorrhage, or fibrin depositing. This results in the reduction in size of the chorionic plate of the placenta, further causing the membranes on the fetal side to fold backward on themselves. The parenchymal villous chorion continues to proliferate beyond the tethered membranes and appears to protrude outward. The fetal blood vessels are directed downward and then horizontally in order to provide blood flow to the most peripheral parts of the placental plate extending beyond the tethered membranes.Since a portion of the placenta tends to become exposed in a circumvallate placenta, due to the reduced size of the chorionic plate, vaginal bleeding is more likely to occur at this site of exposure. Likewise, inhibited fetal growth can also ensue due to the decreased exchange of nutrients and waste between mother and fetus, since the fetus is unable to sustain necessary nutritional demands for proper fetal development. Premature rupture of membranes often occurs as a result of infection in the uterus, which can be caused by the occurrence vaginal bleeding. Therefore, placental abnormalities such as circumvallate placenta can be extremely detrimental in causing the onset of associated conditions. Diagnosis
In some cases, a physician may be able to diagnose a circumvallate placenta via ultrasound during one of many routine ultrasound screenings.