Do psychological flexibility and interparental mutually responsive orientation reduce postpartum parenting stress and coparenting difficulties?

Coparenting is an essential skill, particularly during early childhood; however, increased parenting stress during the postpartum period may undermine parents' abilities to coparent effectively. Research examining protective factors that reduce parenting stress is critical for family well-being. The present study aimed to identify key intrapersonal and interpersonal resources during pregnancy, an ideal intervention period, that are associated with lower levels of postpartum parenting stress to promote adaptive coparenting. A total of 157 mixed-sex couples completed questionnaires and lab tasks during pregnancy and when their child was 1 and 2 years of age. A significant negative association was observed between prenatal parental psychological flexibility (i.e., the ability to accept distressing emotional experiences while maintaining present-moment engagement in behaviors that serve one's values) and postpartum parenting stress, regardless of parent gender. This association was (marginally) stronger to the extent that couples demonstrated high mutual cooperation, attunement, responsiveness, and warmth in their relationship (i.e., mutually responsive orientation [MRO]). Further, across all levels of interparental MRO, (lower) parenting stress at 1 year mediated the link between prenatal psychological flexibility and coparenting quality at 2 years. Psychological flexibility also demonstrated a direct effect on coparenting, independent from parenting stress, suggesting other unmodeled mechanisms, and MRO had a positive interaction with psychological flexibility, suggesting that psychological flexibility might compensate for a lack of MRO to directly promote adaptive coparenting. These findings have important theoretical and clinical implications, highlighting the importance of both intrapersonal (internal) and interpersonal (external) regulatory resources in reducing parenting stress and improving coparenting relationship quality. (PsycInfo Database Record (c) 2025 APA, all rights reserved).