The first available data suggest that rates of many adverse maternal and neonatal outcomes may be lower in women who become pregnant after having a gastric bypass compared with rates in pregnant women who are obese, and with rates in these women before surgery (reduction in gestational diabetes, preeclampsia, low birth weight or macrosomia). In spite of these positive results, there are potential complications during pregnancy directly related to the surgical procedure of gastric bypass. Usual intestinal symptoms of pregnancy (nausea and vomiting during the first trimester, acid reflux, constipation, food intolerance) need to be distinguished from surgical complication, particularly occlusive syndrome. This is a rare event but it could be very serious. In case of abdominal pain, women need to be examined by a digestive surgeon if there is no obstetrical problem. In addition, gastric bypass may result in nutritional deficiencies, in particular iron, vitamin B12, calcium, folic acid, vitamin D and protein deficiencies, because of malabsorption and low food intake. These deficiencies may be pronounced due to food intolerance and increase of physiologic nutritional needs in pregnancy. The frequency of severe deficiencies is limited in women taking vitamin supplements, but their consequences affect both mothers and neonates (such as congenital vitamin B12 deficiency in breastfed infant, or neural tube defect). Folic acid intake should be systematic before pregnancy. Recent recommendations suggest to avoid any pregnancy until weight stabilization (12 to 18 months) after gastric bypass, to screen pregnancy before surgical intervention, to prescribe folic acid supplementation and an efficient contraception right after gastric bypass, to provide support and counseling about diet before or just at the beginning of the pregnancy, to give supplements in iron, folic acid, vitamin B12, calcium and vitamin D. A follow-up on nutrition, if possible with a dietitian in a multidisciplinary team, should be organized once every trimester and in the post-partum period. (C) 2011 Societe francaise de nutrition. Published by Elsevier Masson SAS. All rights reserved.