BEAVER CREEK, COLO. -- Perinatal mortality in infants born following premature rupture of the membranes before 28 weeks' gestation has declined significantly over the past decade, from a rate of 41% in the early 1990s to 19% between 1998 and 2000, Dr. John D. Yeast said during a perinatal conference sponsored by the University of California, Irvine.
In addition, the mortality rate associated with premature rupture of membranes (PROM) before 25 weeks and a period of latency to delivery of more than 14 days fell from 91% in the early 1990s to 25% in 1998-2000, said Dr. Yeast, director of maternal-fetal medicine at St. Luke's Perinatal Center, Kansas City, Mo.
He compared perinatal mortality rates in 81 women with PROM who were seen at St. Luke's from 1998 to 2000 with that in 108 such women seen between 1992 and 1993. Dr. Yeast had reported data on this second group of women previously (Am. J. Obstet. Gynecol. 175:175-81, 1996).
Analysis of the data suggests that mortality is related to gestational age, duration of ruptured membranes, and severity of oligohydramnios, but that no single variable predicts outcome.
In the group of cases from 1998 to 2000, the gestational age at the time of PROM was an average of 2.4 weeks greater in the survivors, compared with the nonsurvivors (25.8 weeks versus 23.4 weeks).
The latency from PROM to delivery was an average 18.4 days in survivors, compared with 11.1 days in nonsurvivors.
The average gestational age at delivery was 28.5 weeks in the survivors and 25.3 weeks in the nonsurvivors. More of the survivors received antenatal steroids than nonsurvivors, 86% versus 67%.
Since many changes have occurred in the way preterm labor and infant prematurity are handled, it is impossible to determine whether any one factor is most responsible for the increased survival, Dr. Yeast said. The women in 1998-2000 generally received short-term tocolysis and, if their pregnancy reached 24-25 weeks, treatment with antenatal steroids. Moreover, neonatal intensive care treatment was aggressive and included surfactant treatment and use of high-frequency ventilation.
PROM accounts for 30%-40% of all premature deliveries, and according to records from St. Luke's Perinatal Center, is the single most common reason for admission to the neonatal intensive care unit.