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Post‐partum interval and time to pregnancy in a prospective preconception cohort
Author(s) -
Willis Sydney K.,
Hatch Elizabeth E.,
Wesselink Amelia K.,
Rothman Kenneth J.,
Mikkelsen Ellen M.,
Ahrens Katherine A.,
Wise Lauren A.
Publication year - 2021
Publication title -
paediatric and perinatal epidemiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.667
H-Index - 88
eISSN - 1365-3016
pISSN - 0269-5022
DOI - 10.1111/ppe.12702
Subject(s) - medicine , pregnancy , fertility , confidence interval , obstetrics , prospective cohort study , demography , gynecology , live birth , cohort , cohort study , post partum , population , environmental health , genetics , sociology , biology
Abstract Background Little is known about the influence of the post‐partum interval—defined as the time between giving birth and attempting to conceive again—on subsequent fecundability. Objectives We evaluated the association between the post‐partum interval and fecundability in Pregnancy Study Online (PRESTO), a web‐based prospective preconception cohort of pregnancy planners from the United States and Canada. Methods Eligible women were aged 21‐45 years, attempting pregnancy, and not using fertility treatment. Women completed a baseline questionnaire to ascertain information on demographics, life style factors, and reproductive history, including detailed information on all previous pregnancies. They completed bi‐monthly follow‐up questionnaires for up to 12 months to update pregnancy status over time. We used proportional probabilities regression models to estimate fecundability ratios (FRs) and 95% confidence intervals (CIs) adjusted for sociodemographic and reproductive history covariates. Analyses were restricted to multiparous women who had been attempting pregnancy with the same male partner for ≤6 menstrual cycles at enrolment. Results During 2013‐2019, 1489 female participants contributed 959 pregnancies and 5003 cycles. The median post‐partum interval was 18 months. Compared with a 12‐ to 23‐month post‐partum interval, FRs for post‐partum intervals of <12, 24‐47, and ≥48 months were 0.89 (95% CI 0.77, 1.04), 1.06 (95% CI 0.91, 1.23), and 0.81 (95% CI 0.62, 1.05), respectively. When restricting to women without a history of subfertility, results were consistent for long post‐partum interval and attenuated for short post‐partum interval. Conclusions Among North American pregnancy planners, long post‐partum intervals (≥48 months) were associated with slightly reduced fecundability. Short post‐partum intervals (<12 months) were weakly associated with reduced fecundability in some subgroups including women with a history of caesarean delivery and planned pregnancies.