Circumvallate placenta is a rare condition affecting about 1-2% of pregnancies, in which the amnion and chorion fetal membranes essentially "double back" on the fetal side around the edges of the placenta. After delivery, a circumvallate placenta has a thick ring of membranes on its fetal surface. Circumvallate placenta is a placental morphological abnormality associated with increased fetal morbidity and mortality due to the restricted availability of nutrients and oxygen to the developing fetus. Physicians may be able to detect a circumvallate placenta during pregnancy by using an ultrasound. However, in other cases, a circumvallate placenta is not identified until delivery of the baby. Circumvallate placenta can increase the risk of associated complications such as preterm delivery and placental abruption. Occasionally, a circumvallate placenta can also increase the risk of neonatal death and emergency caesarean section. Although there is no existing treatment for circumvallate placenta, physicians can attempt to minimize the effects of complications, if they occur, through frequent fetal monitoring and, if necessary, emergency cesarean section.In a circumvallate placenta, the chorionic plate, which forms the fetal surface of the placenta, tends to be smaller than the basal plate, which forms the maternal surface of the placenta. This results in the elevation of the placental margin and the appearance of an annular shape. The fetal surface is divided into a central depressed zone surrounded by a thickened white ring which is incomplete. The ring is situated at varying distances from the margin, or edges, of the placenta.
In the study, a 22-year-old woman at 28 weeks and 2 days of gestation, presented for a routine third trimester screening. She was noted to have had 2 prior miscarriages at 17 and 20 weeks. A previous normal second trimester routine screening at 21 weeks of gestation did not identify any structural abnormalities within the placenta, decreased fetal size, or abnormally-appearing umbilical cord insertion. The patient also did not have any episodes of vaginal bleeding during the current pregnancy.Upon presenting for routine screening at 28 weeks and 2 days of gestation, the patient was not exhibiting any signs of active contractions and a cardiotocography was performed as part of routine screening. Cardiotocography is a diagnostic tool used during the third trimester of pregnancy to observe fetal heart rates and presence of uterine contractions. It can also be used to detect signs of any sort of fetal distress. In interpreting the cardiotocography that the 22-year-old pregnant woman had completed, it was noted that the fetus appeared to be much smaller than expected and was exhibiting concerns of decreased amniotic fluid volume, oligohydramnios, and restricted blood flow through the umbilical cord. Cardiotocographic monitoring also noted decreases in fetal heart rate every 25 minutes without contractions. Fetal motion was present, with the placenta appearing enlarged and spherical.Decreases in the fetus heart rate, in addition to the other findings of the cardiotocography, ultimately prompted physicians to deliver the baby via emergency cesarean section without major complications.