Recurrence rate and outcome of postterm pregnancy, a national cohort study.

OBJECTIVE: To assess the recurrence rate of postterm delivery (gestational age at or beyond 42+0 weeks or 294 days) and to describe maternal and perinatal outcomes after previous postterm delivery.

STUDY DESIGN: From the longitudinal linked Netherlands Perinatal Registry database, we selected all singleton primiparous women who delivered between 37+0 and 42+6 weeks with a subsequent singleton pregnancy from 1999 to 2007. We excluded congenital abnormalities. We compared the recurrence rate of postterm delivery and risk of antenatal fetal death in women with and without a postterm delivery in their first pregnancy. We compared perinatal outcome (composite of perinatal mortality, Apgar score <7 and birth injury) and adverse maternal outcome (composite of maternal death, abruptio placentae, PPH>1000ml and blood transfusions) between women with a recurrent and a de novo postterm second pregnancy.

RESULTS: Our study population consisted of 233,327 women of whom 17,874 (7.7%) delivered postterm in the first pregnancy. In the second pregnancy, 2678 (15%) women had a recurrent postterm delivery compared to 8698 (4%) women with a de novo postterm delivery (odds ratio (OR) 4.2 95% confidence interval (CI) 4.0-4.4). Subgroup analysis in recurrent and de novo postterm delivery showed no differences in composite perinatal and composite maternal outcome (OR 1.0; CI 0.7-1.5, p=0.90 and OR 1.1, CI 0.9-1.4, p=0.16), adjusted for fetal position and mode of delivery).

CONCLUSIONS: Women with a postterm delivery in the first pregnancy have a higher risk of recurrent postterm delivery. Our data suggest that there is no difference in the composite adverse perinatal outcome between recurrent and de novo postterm delivery.