Association Between Birth‐to‐Birth Interval and Postpartum Depressive Symptoms: A Retrospective Cohort Study

AIM: To examine the association between the birth-to-birth interval (BIB) and maternal depressive symptoms at 1 month postpartum, while adjusting for prior postpartum depressive symptoms and other confounders measured during the previous pregnancy. METHODS: We conducted a retrospective cohort study of multiparous women (parity = 2) who delivered their first and second children at a tertiary perinatal center in Japan. The study was restricted to women whose second delivery occurred in 2018-2024 with available outcome data (n = 1144). BIB was defined as the interval in months between the first and second births and was categorized as short (< 24 months), reference (24-59 months), or long (≥ 60 months). The primary outcome was postpartum depressive symptoms, defined as the Edinburgh Postnatal Depression Scale (EPDS) score ≥ 9 at 1 month postpartum. Multivariable logistic regression with multiple imputation (m = 50) was used to estimate adjusted coefficients, adjusting for confounders measured during the previous pregnancy (maternal age, prior-pregnancy EPDS score at 1 month postpartum, use of assisted reproductive technology, body mass index, smoking status, and employment status). RESULTS: Overall, 26.0% (n = 298) and 2.7% (n = 31) of participants had short and long BIBs, respectively. Compared with the reference group, long BIB was associated with higher odds of postpartum depressive symptoms (adjusted OR 5.56; 95% CI, 1.66-18.62), whereas short BIB was not (adjusted OR 1.36; 95% CI, 0.76 to 2.42). CONCLUSIONS: A long but not a short BIB was independently associated with postpartum depressive symptoms at 1 month. Women with a long BIB may benefit from prioritization for early psychosocial support.