In populations where the majority of pregnancies occur to unmarried women, exploring the quality of partner relationships and reproductive health is warranted. This study assesses differences in psychosocial characteristics, health behaviors, and birth outcomes between unmarried pregnant women who reported having a 'good' relationship with their baby's father, compared to those who reported having a 'fair' or 'poor' relationship with their baby's father. This research was part of a prospective study of low-income urban women. All unmarried women (n = 3,633) enrolled during their first prenatal visit were asked questions designed to differentiate between being in a good, fair or poor relationship with the baby's father. The worse the quality of the relationship, the worse the outcome, with dose-response associations between the quality of the relationship, emotional health, health behaviors, and birthweight. Compared to women in good relationships, those in poor relationships were more likely to have depressive symptoms (aPR 1.93; 95% CI: 1.65, 2.25), stress (aPR 1.24; 95% CI: 1.14, 1.35), use drugs (aPR 1.34; 95% CI: 1.11, 1.61) and smoke (aPR 1.28; 95% CI: 1.10, 1.49). Although infants born to mothers in poor relationships had the highest rate of low birth weight, the differences were not significant. Delving beyond marital status to assess the quality of partner relationships among unmarried mothers is important. Further research is needed to understand the complex interplay of individual, social and environmental factors promoting or hindering stable and supportive partner relationships among socially disadvantaged populations of pregnant women.
