The goal of this clinical trial is to test an enhanced version of the National Diabetes Prevention Program (NDPP-NextGen) that is tailored to young women in childbearing years. The investigators will recruit 360 women aged 18-39 years with overweight/obesity who are not currently pregnant, but likely to conceive within 24 months. Women will be randomized to NDPP-NextGen or a usual care control group. The NDPP-NextGen group will participate in the adapted NDPP online group class across 12 months, and the control group will get a packet of information about how to be healthy before, during and after pregnancy. The main goals of the study are: 1. to assess effects of NDPP-NextGen on pre-pregnancy blood sugar and early pregnancy BMI 2. to assess effects of NDPP-NextGen on weight gain and behavioral outcomes during pregnancy 3. to explore effects of NDPP-NextGen on infant's percentage of fat tissue at birth All participants will complete up to 4 research visits: baseline, conception, mid-pregnancy, and delivery. These visits will include: 1. Questionnaires about health, diet, activity, smoking, self-confidence, and depression 2. Body size measurements 3. Fasted blood draws Participants will also be asked to weigh themselves weekly using home scales that are connected to the research database. At the delivery visit, investigators will measure the baby's body size and collect a cord blood sample.