The quality of the interparental relationship bears important implications for children’s socioemotional development. Given evidence that relationship satisfaction among parents tends to decline over time this study examined how change in parents’ relationship satisfaction from nine-months-old until nine-years-old related to children’s socioemotional difficulties at nine-years-old. Participants were 2074 mothers, fathers, and their child (55.1% male) recruited through random sampling of the Child Benefit Registrar by Growing Up in Ireland cohort study. Mothers ranged in age from 18 to 40 years (M = 31.06, SD = 4.70) and fathers ranged in age from 18 to 60 years (M = 33.50, SD = 5.54). Mothers and fathers completed the Dyadic Adjustment Scale at nine-months-old and at nine-years-old whereas child socioemotional development was assessed via teacher report on the Strengths and Difficulties Questionnaire at nine-years-old. Residualised change analysis indicated that both parents experienced declines in relationship satisfaction from nine-months-old until nine- years-old. However, in families where initial levels of relationship satisfaction were high, there was no significant association between decline in satisfaction and child socioemotional difficulties. Conversely, in couples where initial levels of satisfaction were low, mothers, but not fathers, who experienced further declines had female, but not male, children with more socioemotional difficulties at nine years (β = −0.22, p = 0.01; R2 = 0.15, F = 2.31, p = 0.02). These findings highlight the need for carefully tailored interventions aimed at promoting couple relationship satisfaction during transition to parenthood such that the negative impact on children of any decline experienced over time can be mitigated.
