And baby makes four: the stability of coparenting and the effects of child temperament after the arrival of a second child.

This study examined the stability of coparenting and its link to child temperament including 88 families with a firstborn toddler (child 1) that were expecting their second baby (child 2) at T1 (in the last trimester of the second pregnancy). Parents reported on the quality of the coparenting relationship and the temperament of both children. Coparental cooperation was observed at T1 with child 1 and at T3 (when child 2 was 1 year old) with child 1 and 2 in triadic and tetradic contexts. Results show that (a) parent-reported coparenting with child 1 was highly stable; however, this stability was moderated by the difficult temperament of child 2; (b) coparenting with child 1 and child 2 on the basis of parent reports was highly correlated longitudinally and concurrently, although longitudinal links were moderated by the difficult temperament of child 2; and (c) cooperative coparenting observed during triadic interaction at T1 was not linked to cooperation observed when four family members interacted at T3. The study presented here provides further evidence of the plasticity of coparenting in young families and that child temperament plays an important role in shaping the coparenting relationships.