Maternal weight change before pregnancy can be considered as an indicator of maternal energy balance and nutritional status before conception, and may be involved in early life programming. We aimed to investigate the association of maternal Weight Change Before Pregnancy (WCBP) with fetal growth and adverse pregnancy outcomes. Data are from the French EDEN mother-child cohort where 1,756 mother-child pairs had information on mother's weight at 20 years, weight just before pregnancy, fetal anthropometry at second and third trimesters, infant's birthweight and pregnancy complications. The average annual WCBP between 20 years and start of pregnancy (in kg/year) was categorized as: "Weight Loss" (n = 320), "Moderate weight gain" (n = 721) and "High weight gain" (n = 715). The associations of WCBP with fetal and newborn characteristics and with adverse pregnancy outcomes were analyzed, adjusting for maternal and pregnancy characteristics, including the mother's prepregnancy BMI. Interactions between WCBP and prepregnancy BMI were tested. Birthweight and estimated fetal weight in the third trimester increased significantly with increasing WCBP in mothers with BMI <25 kg/m(2). In these mothers, weight loss before pregnancy was associated with a higher risk of newborns small for gestational age (SGA). Whatever the prepregnancy BMI, WCBP was positively associated with a maternal risk of gestational diabetes and hypertension. The ponderal history of mothers before pregnancy can impact on fetal growth and on pregnancy outcomes such as gestational diabetes or hypertension. Our analysis is the first to report that in non-overweight women, those who lost weight before pregnancy are at higher risk of having SGA newborns.