A prospective research evaluating the participation in an educational program, including nutritional support and adequate physical activity, will be offered to overweight and obese pregnant women. The program will last 12 weeks, and will include three workshops on diet of the pregnant and lactating women, and the young child. Physical activity sessions will be offered once a week. Fifteen independent variables likely to influence participation will be analyzed. The association between participation and the risk of maternal and fetal pregnancy complications related to obesity will be analysed. Meanwhile, more fundamental research will be considered to determine of the biological factors involved.