Multipartnered fertility (MPF) is a growing phenomenon in many families and occurs in as many as 74% of couples in certain socio-economic groups (Meyer, Cancian, & Cook, 2005). MPF describes the occurrence of parents having children with more than one partner. As these are often couples that social workers meet in various service environments, understanding their needs is an important consideration for social work practice, policy, and research.

Previous evidence demonstrates that couples with MPF are at an increased risk for unstable relationships (Teachman, 2008a), yet we know little about the timing of relationship dissolution and the differential role that MPF plays in union instability. The primary research question for this study is: “To what extent does multipartnered fertility influence whether and when a couple divorces or separates if they are married, cohabiting, or dating?”

The data (N = 3,022) come from three waves of the Fragile Families and Child Wellbeing Study, a multistage stratified probability sample of hospital births in 20 large U.S. cities. Kaplan-Meier estimates are used to describe the event by illustrating the length of time couples remain in their relationship and to test group differences. Survival analysis using discrete-time models is used to estimate the effects of MPF and covariates on relationship dissolution.

The survivor function suggests a decreasing rate of remaining in the relationship over the study period, especially in father-only and father/mother MPF cases. Furthermore, the hazard function indicates a fast rate of dissolution in the early period following birth, especially among these two groups. The discrete-time models show that father-only and father/mother MPF cases are significantly more likely to end their relationship than couples without MPF, after other factors are accounted for. Moreover, unmarried couples, previously incarcerated fathers, younger mothers, and unsupported mothers are more likely to separate.

Multipartnered fertility among both mothers and fathers may play a critical role in the outcome of couple relationships. The findings from this study suggest that programs and policies to strengthen unmarried couples need to take MPF into consideration, and should carefully consider the timing of interventions to ensure that they are provided at the appropriate time.