Fetal heart rate patterns and fetal distress in patients with preterm premature rupture of membranes.

Two hundred sixty-seven consecutive patients with preterm premature rupture of membranes (PROM) and 130 consecutive patients with idiopathic premature labor and intact membranes between 28 and 35 weeks' gestation were compared. A significantly higher incidence of cesarean section for fetal distress was found in patients with PROM (7.9%) compared with patients with premature labor (1.5%) (P less than .05). Fetal distress occurred with similar frequency in patients with and without chorioamnionitis. Analysis of electronic fetal heart rate patterns in patients with fetal distress revealed that 16 of 21 patients (76%) with PROM had patterns consistent with umbilical cord compression. A significant difference was found in neonatal mortality rates between the PROM group (4.5%) and the premature labor group (0) (P less than .05). The neonatal death rate in patients with fetal distress (three of 12) was significantly higher than in patients without distress (nine of 385) (P less than .01). It is suggested that the increased incidence of fetal distress in patients with preterm PROM may represent the loss of the protection of the umbilical cord that amniotic fluid normally provides.