Cesarean delivery, labor duration, and mothers' mortality risk over 50 years of follow-up

Abstract

Background: Pregnancy complications have been recognized as a window to future health. Though cesarean delivery is common, it is unknown whether labor duration and mode of delivery are associated with maternal long-term mortality.

Objective: To examine whether labor duration and mode of delivery were associated with all-cause and cause-specific mortality.

Study design: Participants were mothers from the multisite Collaborative Perinatal Project (CPP) cohort (1959-1966; n=43,646, limited to last CPP delivery). We ascertained all-cause and specific causes of death as of 2016 via linkage to the National Death Index and Social Security Death Master File. Hazard ratios (HR) testing mode of delivery and labor duration were estimated using Cox proportional hazards models adjusted for demographic and clinical characteristics. We further stratified analyses by parity.

Results: Among participants with a recorded delivery mode, 5.9% (2486/42,335) had a cesarean delivery. Participants who had a cesarean were older (26.9 vs 24.3 years), with higher body mass index (24.0 vs 22.7 kg/m²), were less likely to be nulliparous (21% vs 30%), and more likely to have a household income of at least $6000 (22% vs 17%), to smoke ≥1 pack/d (18% vs 15%), to have diabetes mellitus (12% vs 1%) and to have a prior medical condition (47% vs 34%), compared to participants with a vaginal delivery. Delivery mode was similar by race/ethnicity, marital status, and education. Median labor duration was 395 minutes among participants who had an intrapartum cesarean delivery and 350 minutes among participants delivered vaginally. By 2016, 52.2% of participants with a cesarean delivery and 38.5% of participants with a vaginal delivery had died. Cesarean vs vaginal delivery was significantly associated with increased risk for all-cause mortality (HR=1.16 (95% confidence interval [CI]: 1.09, 1.23); in nulliparas, HR=1.27 (95% CI: 1.09, 1.47); in multiparas, HR=1.13 (95% CI: 1.06, 1.21) as well as increased risk of death from cardiovascular disease, diabetes, respiratory disease, infection, and kidney disease. Associations with death from cardiovascular disease, infection, and kidney disease were stronger for multiparas than nulliparas, though the association with death from diabetes was stronger among nulliparas. Labor duration was not significantly related to overall mortality.

Conclusion: In a historic United States cohort with a low cesarean delivery rate, cesarean delivery was an indicator for subsequent increased mortality risk, particularly related to cardiovascular disease and diabetes. Future studies with long-term follow-up are warranted given the current high prevalence of cesarean delivery.

Keywords: Collaborative Perinatal Project; epidemiology; maternal mortality; mode of delivery.