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

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.

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.

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).

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.