Trajectories of Perinatal Depressive Symptoms from the Second Trimester to Three Months Postpartum and Their Dynamic Relationship with Social Support: A Prospective Cohort Study in Beijing, China.

Purpose: Social support has long been recognised as one of the most important extrinsic factors influencing perinatal depressive symptoms, yet few cohort studies have simultaneously tracked changes in both domains. This study aimed to identify heterogeneous trajectories of depressive symptoms and to examine their dynamic association with social support across the perinatal period. Patients and Methods: A prospective cohort study was conducted in Beijing, enrolling participants at 15 gestational weeks. Depressive symptoms were assessed using the Edinburgh Postnatal Depression Scale (EPDS), and social support was measured with the Social Support Rating Scale (SSRS) at five time points from enrolment to three months postpartum. A total of 1416 women completed at least three assessments. The overall trajectory of depressive symptoms was estimated using LGCM, and LCGM was used to identify heterogeneous subgroups. The association between depressive symptoms and social support over time was examined using a parallel-process growth model. Results: The overall EPDS trajectory showed a progressive increase from mid-pregnancy to three months postpartum. Two latent trajectories were identified: an ascending-low symptom group (72.2%) with initially low but gradually increasing symptom levels, and a persistently elevated symptom group (27.8%) with persistently elevated symptoms. After accounting for social support, the overall trajectory flattened into a stabilized linear pattern. In subgroup analyses, higher symptom levels were observed in both groups in models not accounting for social support; notably, the formerly ascending-low symptom group transformed into a stable linear trajectory at a higher level. Conclusion: From 15 weeks of gestation to three months postpartum, perinatal depressive symptoms showed an overall increasing trend. However, substantial heterogeneity was observed: approximately 70% of women followed an ascending-low symptom trajectory, whereas about 30% exhibited persistently elevated symptoms with minimal change over time. Higher social support was associated with less worsening of depressive symptoms over the perinatal period, and this association appeared stronger during pregnancy than postpartum, particularly among women with lower initial symptom levels. These findings suggest that strengthening social support across pregnancy and the postpartum period may contribute to mitigating symptom worsening and promoting improved maternal mental health.