Circumvallate placenta

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. This thick ring of membranes is composed of a double fold of amnion and chorion with degenerated decidua vera and fibrin in between. Blood vessels, supplying nutrients and carrying waste products to and from the developing fetus, radiate from the umbilical cord insertion to as far as the ring of membranes, and then disappears from view.

A circumvallate placenta does not always induce associated symptoms during pregnancy, making it extremely difficult to diagnose a circumvallate placenta in asymptomatic mothers. In symptomatic mothers, physicians may be able to detect a circumvallate placenta based on the presentation of the following signs.

Circumvallate placenta has also been associated with a higher incidence of complications including placental abruption, low birth weight, premature delivery, perinatal death, and fetal abnormalities.

Unfortunately, there is no known cause of circumvallate placenta and no major preventative measures that can be taken to minimize the risk of developing a circumvallate placenta. Circumvallate placenta is not a genetic disorder. Some potential causes of circumvallate placenta include reduced amniotic fluid pressure, circumferential hemorrhage, and superficial or deep implantation of the embryo within the uterine wall, although these potential causes are still not well-understood in terms of their relation to circumvallate placenta.

High-risk pregnancies are described as pregnancies in which a mother, the fetus, or both are put at a higher risk for developing pregnancy complications before, during, or after birth. Risk factors such as hypertensive medical conditions, maternal age, and substance use are just some of the things that can put a woman at an increased risk for developing circumvallate placenta and/or any other complications.

Women entering a pregnancy with hypertension are considered to be put at a higher risk for preeclampsia or eclampsia during the course of their pregnancy. Hypertensive disorders, like hypertension, have been found to affect about 10% of pregnancies in the United States and have resulted in about 6.8% of maternal deaths from 2011 to 2015. High blood pressure during pregnancy can potentially damage maternal organ systems such as the liver or the kidneys, which can be life-threatening. To prevent preeclampsia or eclampsia from developing in pregnancy, women with hypertension can be prescribed anti-hypertensive medications during pregnancy and are advised to monitor their blood pressure throughout the course of pregnancy.