Impact of prenatal maternal depression on gestational length: post hoc analysis of a randomized clinical trial

Background Shortened gestation is a leading cause of childhood morbidity and mortality with lifelong consequences for health. There is a need for public health initiatives on increasing gestational age at birth. Prenatal maternal depression is a pervasive health problem robustly linked via correlational and epidemiological studies to shortened gestational length. This proof-of-concept study tests the impact of reducing prenatal maternal depression on gestational length with analysis of a randomized clinical trial (RCT). Methods Participants included 226 pregnant individuals enrolled into an RCT and assigned to receive either interpersonal psychotherapy (IPT) or enhanced usual care (EUC). Recruitment began in July 2017 and participants were enrolled August 10, 2017 to September, 8 2021. Depression diagnosis (Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition; DSM 5) and symptoms (Edinburgh Postnatal Depression Scale and Symptom Checklist) were evaluated at baseline and longitudinally throughout gestation to characterize depression trajectories. Gestational dating was collected based on current guidelines via medical records. The primary outcome was gestational age at birth measured dichotomously (≥39 gestational weeks) and the secondary outcome was gestational age at birth measured continuously. Posthoc analyses were performed to test the effect of reducing prenatal maternal depression on gestational length. This trial is registered with ClinicalTrials.gov (NCT03011801). Findings Steeper decreases in depression trajectories across gestation predicted later gestational age at birth, specifically an increase in the number of full-term babies born ≥39 gestational weeks (EPDS linear slopes: OR = 1.54, 95% CI 1.10–2.16; and SCL-20 linear slopes: OR = 1.67, 95% CI 1.16–2.42). Causal mediation analyses supported the hypothesis that participants assigned to IPT experienced greater reductions in depression symptom trajectories, which in turn, contributed to longer gestation. Supporting mediation, the natural indirect effect (NIE) showed that reduced depression trajectories resulting from intervention were associated with birth ≥39 gestational weeks (EPDS, OR = 1.65, 95% CI 1.02–2.66; SCL-20, OR = 1.85, 95% CI 1.16–2.97). Interpretation We used a RCT design and found that reducing maternal depression across pregnancy was associated with lengthened gestation. Funding This research was supported by the NIH (R01 HL155744, R01 MH109662, R21 MH124026, P50 MH096889).