ObjectivesThe objective is to to explore the longitudinal change trajectories of postpartum stress and its related factors.DesignA longitudinal study with follow-ups from 42 days to 6 months after delivery.Settings and participantsA total of 406 postpartum women were recruited at baseline (42 days after delivery) from 6 hospitals in Nantong, Jiangsu Province, China, and followed up at 3 and 6 months. After the follow-ups, 358 postpartum women were retained for further analysis.MethodsPostpartum stress was evaluated using the Maternal Postpartum Stress Scale (MPSS) at baseline (42 days) and 3 and 6 months after delivery. MPSS has three dimensions, such as: personal needs and fatigue, infant nurturing and body changes and sexuality. Postpartum depression and anxiety were measured using the Edinburgh Postnatal Depression Scale and the short-form Depression, Anxiety and Stress Scale, respectively. The MPSS scores were normalised using a rank-based inverse normal transformation.ResultsPostpartum stress decreased significantly after 3 months, and postpartum stress reduced further after 6 months. Additionally, the scores for all three dimensions reduced after 6 months, while infant nurturing reduced after both 3 and 6 months. Older age (β=0.028, p=0.049), higher education level (β=0.153, p=0.005) and higher body mass index (BMI) (β=0.027, p=0.008) of the postpartum women were significantly associated with higher postpartum stress levels in corresponding dimensions at 42 days. Older age was also associated with higher postpartum stress at 3 (β=0.030, p=0.033) and 6 months (β=0.050, p<0.001) in the dimension of personal needs and fatigue. Postpartum stress levels were significantly higher in women with depression or anxiety symptoms.ConclusionsPostpartum stress continuously declined from 42 days to 6 months after delivery. Postpartum women with older age, higher education levels, higher BMI and anxiety or depression symptoms should be the target population for early intervention.