This study will examine the safety and effectiveness of a dietary intervention in pregnant women. Women who are obese will be invited to participate. The control arm will receive routine prenatal care and one in-person nutritional and dietary counseling session to promote healthy eating during their pregnancy. The intervention arm will receive a more intensive dietary program that will include in-person counseling and group support sessions. The goal of the intervention will be weight maintenance (weight at 2 weeks after delivery should be within 3% of baseline weight) and avoidance of postpartum weight retention