Introduction Scarce research is available regarding the association between interbirth intervals (IBI) and long-term maternal health outcomes, particularly cardiovascular disease (CVD) mortality. We aimed to assess whether IBIs were associated with all-cause, CVD-related and cancer-related mortality.
Methods We conducted a cohort study in the setting of the Jerusalem Perinatal Study. Women with at least two consecutive singleton live births in 1964–1976 (N=18 294) were followed through 2016. IBIs were calculated as the interval between women’s first and second cohort birth. We estimated associations between IBIs and mortality using Cox’s proportional hazards models, adjusting for age, parity, maternal education, maternal origin and paternal socioeconomic status. Date of last menstrual period was available for a subset of women. We assessed the interpregnancy interval (IPI) for these women and compared the models using IPI and IBI.
Results During 868 079 years of follow up (median follow-up: 49.0 years), 3337 women died. Women with IBIs <15 months had higher all-cause mortality rates (HR 1.18; 95% CI 1.05 to 1.33) compared to women with 33-month to 68-month IBIs (reference category). IBI and CVD mortality appeared to have a J-shaped association; IBIs of <15, 15–20, 21–2626–2632, 33–68 and ≥69 months had HRs of 1.44, 1.40, 1.33, 1.14, 1.00 and 1.30, respectively. No substantial association was found with cancer mortality. Models using IPIs and those using IBI were similar.
Conclusion Our results support the WHO recommendations for IPIs of ≥24 months and add additional evidence regarding long-term CVD mortality.
- MATERNAL HEALTH
- SOCIAL INEQUALITIES
- Lifecourse/ Childhood Circumstances
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Contributors YLW, OM and RC-M conceived and designed the study; OM, YF, HH and OP collected the data; YLW, OM and RC-M contributed to data or analysis tools; YLW performed the analysis; YLW wrote the paper, with considerate input from OM, YF, HH, OP and RC-M.
Funding Yiska Loewenberg Weisband is grateful to the Azrieli Foundation for the award of an Azrieli Fellowship. The Azrieli Foundation had no role in the design, analysis or writing of this article.
Competing interests None declared.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon reasonable request.