The transition to parenthood brings a host of changes to new parents; two key areas of change are decreases in relationship functioning and a worsening of women's eating, weight, and shape (EWS) concerns. Past research has suggested that a connection may exist between women's EWS concerns and relationship functioning during this transition. This study explored the impact of women's EWS concerns on both partners' relationship functioning in a sample of 74 couples (148 individuals) having their first baby. The study was part of a larger project exploring interventions during the transition to parenthood; thus, all couples had at least one risk factor for future relationship problems. Participants completed questionnaires approximately seven months into pregnancy and at one and three months postpartum. Results revealed that relationship functioning and women's EWS concerns worsened from pregnancy to three months postpartum, which is consistent with previous literature. Changes in women's EWS concerns from before and during pregnancy to three months postpartum were not generally related to changes in either partner's relationship functioning during the same period. However, the EWS concerns that predicted poorer relationship outcomes, including women's drive for thinness and bulimia symptoms, suggest the possible role of third factors such as negative affect or neuroticism. Also, increases in women's Body Mass Index from pre-pregnancy to three months postpartum predicted increases in relationship functioning, indicating the possibility of a larger construct such as general acceptance of the post-birth process, both in terms of weight changes and relationship changes. Thus, preventive efforts could include an emphasis on helping partners to accept the changes they will experience during this transition. Finally, the significant relations between women's EWS concerns and relationship functioning were often mediated by men's reported frequency of sexual activity, suggesting the importance of sex as a mediator. Although findings were limited, the results should be interpreted in light of previous research and the current study's limitations. Overall, this study indicates the need for future research exploring the relations between women's EWS concerns and the couple relationship during the transition to parenthood.