Couples expecting their first child were randomly assigned to intervention (n = 28) and comparison groups (n = 38) to assess the efficacy of a couples intervention and examine marital satisfaction trajectories across the transition to parenthood. The primarily European American sample (M age = 30 years) completed assessments of marital satisfaction at 5 points from the final trimester of pregnancy to 66 months postpartum. Growth curve analyses indicated a normative linear decline in marital satisfaction. Intervention participants experienced significantly less decline than comparison participants, providing support for the efficacy of the intervention. Comparable childless couples (n = 13) did not show a decline in marital satisfaction. The results suggest that early family transitions that strain couple relationships provide critical opportunities for preventive interventions to strengthen marriage.