Lifestyle interventions targeting overweight individuals can produce positive ripple effects on untreated overweight partners in the home. Interestingly, ripple effects on partners' weight appear most pronounced when the interventions target women. Women, and mothers in particular, remain the primary nutritional gatekeepers of the home. Despite widespread recognition that motherhood is a powerful motivator for behavior changes, no study to date has examined the ripple effects of prenatal lifestyle interventions that target mothers' gestational weight gain. The primary aim of the proposed study is to determine whether lifestyle interventions to prevent excessive gestational weight gain in overweight/obese pregnant women have positive ripple effects on untreated partners in the home. The proposed study is ancillary to two randomized phase III clinical trials in the LIFE-moms consortium (1U01HL114377-01, PI Phelan; 3U01DK094418-01S1, PIs Martin and Redman) that are examining the efficacy of multi-component lifestyle interventions to prevent excessive gestational weight gain in a total of 650 overweight/obese women. In this ancillary study, partners' weight, home environment, and psychosocial behaviors will be assessed when their pregnant partners are ~13 weeks gestation (study entry), 35 weeks gestation and at 6 and 12 months postpartum. We hypothesize that partners of pregnant women randomized to the lifestyle intervention, relative to those of standard care, will have greater weight losses through 12-months. Secondary aims examine partner improvements in weight control behaviors, the home environment, and psychosocial parameters. This project is highly innovative, as it capitalizes on existing funded research and is the first study to examine ripple effects of multicomponent prenatal interventions. The project also has high impact, as pregnancy is a powerful motivator for behavior and environmental changes in the home; and, if positive ripple effects occur, the field of obesity treatment and prevention could move beyond focus on individual level to the often unrecognized interpersonal effects of lifestyle interventions.