Association of Vasa Previa at Delivery With a History of Second-Trimester Placenta Previa

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Vasa previa is a rare obstetric disorder characterized by velamentous insertion of the fetal vessels over the mouth of the cervix. Reported fetal mortality estimates range from 58% to 73%. Ultrasonography has proved helpful for diagnosing this condition prenatally, improving outcomes, but little is known about any antecedent conditions that predispose to vasa previa. This study evaluated 1 possible factor, a history of second-trimester placenta previa, in 13 women presenting with vasa previa in the years 1991 through 2001. Deliveries totalled nearly 73,000 during this period. Vasa previa occurred once in every 5614 deliveries. Four control women with normal placentation were matched with each study patient. Eight of the 13 cases were detected in the third trimester by demonstrating fetal blood flow over the cervical os using pulsed color flow Doppler ultrasonography. Two other women presented at the time of amniotomy during labor with acute vaginal bleeding and subsequent fetal bradycardia. In 2 cases, the fetal vessels were palpated within the amniotic membranes during labor. One case was diagnosed after delivery, the fetus having died; torn fetal vessels were found when viewing the placenta. This woman had undergone membrane stripping during a prenatal visit at 41 weeks gestation. Three of the 13 women with vasa previa were nulliparous. Demographic features were similar in the study and control groups, although affected women tended to be older and to have undergone dilation and curettage more often than control women. Antepartum vaginal bleeding, cesarean delivery, and cesarean hysterectomy all were more frequent in study women. Two women, including the 2 with a dead fetus, were delivered vaginally. Nine of 13 women (69.2%) had placenta previa diagnosed by midtrimester ultrasonography. This was true for only 2 control women (3.8%), making the association highly significant. This retrospective study disclosed a statistically impressive relationship between vasa previa at delivery and a history of second-trimester placenta previa. Prospective studies of women with the latter condition would be of interest.