Using family systems theory and a dyadic growth curve, the authors examined factors associated with a smooth versus rocky transition to parenthood for 125 couples. The authors identified significant variability in couples' experiences. Although many parents reported declines in love and increases in conflict, 23% of mothers and 37% of fathers reported equal or increased love; 20% of mothers and 28% of fathers reported equal or lower conflict. Fathers of reactive infants reported higher levels of conflict, and fathers of daughters reported increasing conflict over time. Fathers' marital love decreased when their expectations were violated, and fathers' conflict increased when mothers reported violated expectations. Finally, mothers' marital conflict increased with greater changes in depressive symptoms. Despite potential gender differences, within-couple analyses showed synchrony between partners suggesting that potential gender differences may be best treated within the couple.