The concern about obesity in children has increased worldwide. The question arises, whether this trend to obesity already starts during the prenatal period and to what extent the increase of weight is related to a secular trend in height.For neonatal data, three studies, performed in The Netherlands, with neonatal data of birth weights were compared. For postnatal data, weight, height and body mass index (BMI) of two nationwide studies, performed in the Netherlands, were analyzed.No differences between birth weights were found between 1970 and 2007. In postnatal data a trend of increasing weight and BMI in both boys and girls starts from five years onwards. The secular trend in height starts from the age of two and a half years onward in both boys and girls. The increase in weight is more pronounced than the increase in height.No prenatal secular trend could be detected in The Netherlands. Postnatal, the secular trend is obvious for weight, height and BMI. The increase in skewness of the weight distribution may be ascribed to a metabolic disturbance of the population.