If a mother is obese during pregnancy, her offspring will also be at increased obesity risk. This might be explained by the hypothesis that environmental factors in the womb program the fetus for increased obesity risk later. However, the correlation between the mother’s and offspring’s body mass index (BMI) could also be due to genetic variation that is shared by the mother and offspring. If this is the case then interventions to reduce the BMI of mothers before pregnancy in order to reduce the obesity risk of the offspring may be less effective. Preliminary data from the Northern Finland Birth Cohorts suggest that genetics may explain a large part of the correlation between mother’s and offspring’s BMI. This project aims to use ALSPAC data to i) provide an independent replication of the results from the Northern Finland Birth Cohorts (using the Bivariate Genome Wide Complex Traits Analysis (GCTA) statistical model) and ii) account for maternal genetic factors by offering the opportunity to perform maternal genome wide complex trait analysis.