Healthy diet in pregnancy should guarantee proper fetal growth and development, maintain (and promote) maternal health and enable lactation. Nutritional counseling and interventions need to be an integral part of antenatal care and continue during pregnancy in order to reduce the risk of maternal, fetal and neonatal complications, as well as the short- and long-term adverse outcomes. Adverse pregnancy outcomes are more common in women who begin the gestation as undernourished or obese in comparison to pregnant women whose weight is within normal ranges. Increased nutritional and energy needs in pregnancy are met through numerous metabolic adaptations; pregnancy is successfully achieved within wide range of variations in energy supply and weight gain. However, if nutrient restriction exceeds the limits of adaptive responses, evidence indicates that fetus will develop the alternative metabolic competence that might emerge as a disease (type 2 diabetes, hypertension, coronary heart disease and stroke) in adult life.