Risk for postterm delivery after previous postterm delivery

Abstract

We examined the hypothesis that the risk for subsequent postterm birth is increased in women with an initial postterm birth. We performed a population-based cohort study of Missouri births (1989-1997) to assess the recurrence of postterm birth using the Missouri Department of Health's maternally linked database. A total of 368,633 births were evaluated, of which 7.6% were postterm (>42 weeks of gestation). Black mothers had a lower risk for all (adjusted odds ratio [OR], 0.70; 95% CI, 0.67-0.73) or recurrent (adjusted OR, 0.73; 95% CI, 0.67-0.79) postterm birth. Maternal education of <12 years (adjusted OR, 1.51; 95% CI, 1.41-1.62), indices of low socioeconomic status, and maternal body mass index >35 kg/m2 (adjusted OR, 1.23; 95% CI, 1.11-1.37) were associated with increased risk for recurrent postterm birth. Mothers with an initial postterm birth were at increased risk for postterm birth (OR, 1.88; 95% CI, 1.79-1.97) in subsequent pregnancies, independent of race. Among mothers who deliver postterm, there is a significant risk for subsequent postterm births. This increased risk suggests that common factors (genetic or other) influence the likelihood of abnormal parturition timing.