Objectives: Successful gestational weight gain (GWG) restriction programs for obese (Body Mass Index (BMI) amp;gt;= 30 kg/m(2)) pregnant women, have not, so far, shown convincing effects on infants weight development. An intervention starting during the pregnancy might be too late and a pre-conceptional life style change may be preferable. Thus, the aim of this study was to follow children born to mothers who had participated in a weight gain restriction program during pregnancy, and make comparisons with their younger siblings. Study design and main outcome measures: An extended analysis of 262 children belonging to an intervention group and a control group. The effects of BMI at five years of age and weight-for-length/height development from two months of age until five years of age were assessed. Results: In the intervention group there was a difference in BMI at five years of age, between index boys and their younger sisters (p = 0.016). Mean BMI was lower among the boys compared with their younger female siblings. Regarding maternal GWG or the Swedish national reference data there was no difference between the index children and their younger siblings within the intervention or control groups or between younger siblings in the two groups. Conclusions: Maternal pre-conceptional lifestyle change may have a positive effect on the childs weight development during the five first years of age. However, the effect of participation in an extensive GWG restriction program when it comes to the impact on the offsprings weight development is still unclear and further research is required.