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

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  weeks and 37  weeks. Women with >1 spontaneous PTB were included only once. Unexposed women had all deliveries at or beyond 38  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.