Background: First‐time mothers commonly experience stress and depressive symptoms in the postpartum period. Maternal self‐efficacy has been shown to be an important protective factor against these experiences; however, research on the dynamic nature of stress, depressive symptoms, and maternal self‐efficacy is limited. The aim of this study was to document changes in these psychological factors among first‐time mothers, and determine how early maternal self‐efficacy perceptions may predict change in stress and depressive symptoms over the first 6 months postpartum. Methods: Sixty first‐time Australian mothers were recruited during their third trimester of pregnancy. Participants completed a baseline survey during the third trimester of pregnancy ( M  =   32.87 weeks, SD = 2.62 weeks), and subsequently reported stress, depressive symptoms, and maternal self‐efficacy every 3 weeks postpartum for 6 months. Latent growth curve modelling was used to estimate participants’ change over time for stress and depressive symptoms. Results: First‐time mothers’ stress and depressive symptoms peaked, and maternal self‐efficacy was weakest, at 3 weeks postpartum. Maternal self‐efficacy at 3 weeks postpartum was a significant (negative) predictor of 3‐week levels of, and also (positively) predicted later reductions in, stress. Conclusion: Future interventions aimed at bolstering early maternal self‐efficacy may protect against postpartum stress for first‐time mothers.

(1) Background: The transition to motherhood can be challenging, especially for first-time mothers, and can accompany maternal distress. Social support—such as that offered by peers—can be important in assisting mothers to manage such distress. Although primiparous mothers often seek out and value peer support programs, few researchers have investigated factors that may influence the strength of relationships in non-professional maternal peer support programs. Insight into these factors can be key to enhancing the success of future peer support interventions. (2) Methods: Reflexive thematic analysis was applied to data gathered from 36 semi-structured interviews conducted with 14 primiparous mothers and 17 peer mentors in a peer support program. (3) Results: Four themes related to successful mentorship were identified: expectations of peer relationship, independence of peer mentor, contact, and similarities. (4) Conclusions: For primiparous mothers who are developing their support network, these factors appear important for promoting close and effective peer support relationships. Interventions that harness the dynamics between these factors may contribute to more successful peer support relationships and mental health outcomes for participants.