The gestational period represent a critical time for influencing birth weight, infant adiposity and growth rate, all of which are important factors in the development of obesity and diabetes in adolescence and adulthood. Prior to pregnancy, the nutritional status and weight of a mother also has significant influence on these factors. During gestation, numerous maternal factors can have a negative influence on programming of the long-term health of the offspring. Rate of maternal weight gain, glucose intolerance, gestational diabetes and pre-pregnancy BMI all have significant influence on infant size and adiposity at birth. Additionally, these factors are related to the development obesity and its co-morbidities in adolescence and adulthood. Given the rates of obesity and associated health care costs, it is very timely to understand possible fetal origins of obesity and diabetes to help shape interventions.