Obstetrics & Gynecology>>>>>Maternal-Fetal Physiology and Placentation
Question 5#

A 22-year-old G1P0 at 28 weeks’ gestation by LMP presents to labor and delivery complaining of decreased fetal movement. She has had no prenatal care. On the fetal monitor there are no contractions. The fetal heart rate is 150 beats per minute and reactive, with no decelerations in the fetal heart tracing. An ultrasound demonstrates a 28-week fetus with normal anatomy and size consistent with menstrual dates. The placenta is implanted on the posterior uterine wall and its margin is well away from the cervix. A succenturiate lobe of the placenta is seen implanted low on the anterior wall of the uterus. Doppler flow studies indicate a blood vessel is traversing the cervix connecting the two lobes.

This patient is most at risk for which of the following?

a. Premature rupture of the membranes
b. Fetal exsanguination after rupture of the membranes
c. Torsion of the umbilical cord caused by velamentous insertion of the umbilical cord
d. Amniotic fluid embolism
e. Placenta accreta

Correct Answer is B

Comment:

This patient has a vasa previa. When fetal vessels cross the internal os (vasa previa), rupture of membranes may be accompanied by rupture of a fetal vessel leading to fetal exsanguination. Vasa previa does not increase the risk for placenta accreta or amniotic fluid embolism. With velamentous insertion of the cord, the umbilical vessels separate in the membranes at a distance from the placental margin which they reach surrounded only by amnion. Such insertion occurs in about 1% of singleton gestations but is quite common in multiple pregnancies. Fetal malformations are more common with velamentous insertion of the umbilical cord. An increased risk of premature rupture of membranes and torsion of the umbilical cord has not been described in association with velamentous insertion of the cord.