Long-term maternal mortality risk following spontaneous preterm birth: A retrospective cohort study

Abstract

Objective: To determine whether women with spontaneous preterm birth (PTB) have increased risks for long-term mortality.

Design: Retrospective cohort.

Setting: Births in Utah between 1939 and 1977.

Population: We included women with a singleton live birth ≥20 weeks who survived at least 1 year following delivery. We excluded those who had never lived in Utah, had improbable birthweight/gestational age combinations, underwent induction (except for preterm membrane rupture) or had another diagnosis likely to cause PTB.

Methods: Exposed women had ≥1 spontaneous PTB between 20⁺⁰ weeks and 37⁺⁰ weeks. Women with >1 spontaneous PTB were included only once. Unexposed women had all deliveries at or beyond 38⁺⁰ weeks. Exposed women were matched to unexposed women by birth year, infant sex, maternal age group and infant birth order. Included women were followed up to 39 years after index delivery.

Main outcome measures: Overall and cause-specific mortality risks were compared using Cox regression.

Results: We included 29 048 exposed and 57 992 matched unexposed women. There were 3551 deaths among exposed (12.2%) and 6013 deaths among unexposed women (10.4%). Spontaneous PTB was associated with all-cause mortality (adjusted hazard ratio [aHR] 1.26, 95% confidence interval [CI] 1.21-1.31), death from neoplasms (aHR 1.10, 95% CI 1.02-1.18), circulatory disease (aHR 1.35, 95% CI 1.25-1.46), respiratory disease (aHR 1.73, 95% CI 1.46-2.06), digestive disease (aHR 1.33, 95% CI 1.12-1.58), genito-urinary disease (aHR 1.60, 95% CI 1.15-2.23) and external causes (aHR 1.39, 95% CI 1.22-1.58).

Conclusions: Spontaneous PTB is associated with modestly increased risks for all-cause and some cause-specific mortality.

Keywords: follow-up studies; lifecourse; premature birth; retrospective studies; women's health.