Several studies show that maternal BMI before conception and during pregnancy predict future risk of obesity and associated metabolic conditions for both mother and offspring. Weight gain during the first two years of life is also critical, not only to ensure infant survival, but also in defining the infant's predisposition to the emergence of chronic diseases during adulthood. From a population perspective, the most effective approach to counteract the epidemic of obesity and NCDs is to prevent them. Recommendations for healthy diets and physical activity during pregnancy and infancy, as well as monitoring of nutrition goals are currently available in the Chilean primary health care system. However, most of these recommendations are not up to date and virtually all are poorly implemented. Objective: to assess the effectiveness of delivering (via primary health centers) an intervention that enhances compliance with up to date nutrition and health care standards (regarding diet, physical activity and breastfeeding promotion) during pregnancy and the first year of life. The main goal is that mothers achieve adequate nutritional status & metabolic control, during and early after pregnancy, and that infants grow and develop healthily (adequate linear and ponderal growth according to WHO standard, while avoiding excess BMI gains) Methods: this is a cluster randomized controlled trial (CRCT), designed as a public health "program effectiveness" study (i.e. intervention will be available through the established national health system under standard operating conditions). The cluster units will be 12 primary health care centers (PHCC) in South-East Santiago randomly allocated to: 1) enhanced nutrition and health care standards (intervention group) or 2) routine care (control group).