Drawing on the relational turbulence model, this study queries whether it is the amount of relational uncertainty and partner interference in a relationship, or the magnitude of an increase in these mechanisms over time, that accounts for decreased relationship satisfaction for new parents. To test these competing hypotheses, a longitudinal study of 78 couples was conducted in which both partners completed surveys about their relationship at 4 time points during the transition to parenthood. Multilevel modeling revealed that the amount and the increase of relational uncertainty and partner interference were negatively associated with relationship satisfaction when considered separately, but when evaluated in combination, the magnitude of an increase in these variables was the stronger predictor of relationship satisfaction.