The purpose of this study is to determine whether an intervention combining motivational interviewing and follow-up with a mobile phone application will help overweight women and their partners adopt healthy lifestyle habits in the preconception period. This study will also evaluate the impact of the intervention on the weight, waist circumference, and body fat of women and their partners. Women and their partners will be followed through pregnancy to explore the effects of the intervention on the adequacy of gestational weight gain, rates of pregnancy complications, delivery mode, and infant birth weight.