Inter-birth Intervals and All-Cause, Cardiovascular and Cancer-related Mortality: Findings from a Population-based Cohort

Background: Short and long inter-birth intervals (IBI) are associated with adverse neonatal and maternal outcomes; however, little is known regarding long-term effects on maternal health. We aimed to assess whether IBIs were associated with all-cause, CVD-related and cancer-related mortality.

Methods: The Jerusalem Perinatal Study cohort includes all births to residents of Jerusalem in 1964-1976. Follow-up data on all-cause and cause-specific mortality through 2016 was obtained via record linkage. This study included women who had at least two singleton births (N=18,538, total person-years=880,399, number deaths=3,375). We calculated intervals between women’s first and second birth in the cohort, and minimum intervals between births, as both continuous and categorical variables. We used Cox’s proportional hazards models to estimate associations between IBIs and mortality, adjusting for age, parity, education, origin, and socioeconomic status.

Results: In this highly parous population (median parity=4), women with IBI under 15 months 1.15, 95% CI 0.96 – 1.37).

Discussion

In this large population-based study with long follow-up, IBI was inversely associated with all-cause mortality, and short IBI was associated with increased risk of CVD-related mortality. These findings suggest that women with longer IBIs may have sufficient time to recover from the physiological stress of previous pregnancies, leading to reduced CVD mortality.