Adriëtte Oostvogels

9 Interpretation of the results Pathways in the prenatal period Maternal pBMI is a predictor of offspring’s overweight and cardiometabolic profile in childhood. 23-29 The studies in this thesis support these findings, in particular for offspring’s body composition and cardiometabolic profile at age 5-6 years. Although this thesis shows that, in accordance with the literature, women with overweight have a more atherogenic lipid profile throughout pregnancy, 30-32 maternal early pregnancy lipid profile did not mediate the association between maternal pBMI and offspring’s cardiometabolic profile in childhood. Nonetheless, the independent positive associations of maternal early pregnancy lipid profile and offspring’s body composition and lipid profile, suggest that maternal lipid profiles could program offspring’s body composition and lipid profile Since maternal lipid profile is a factor that can be modified through e.g. diet interventions or physical activity, it could be a target for preventive strategies to optimise offspring’s health. It remains unclear whether the mechanism through which maternal overweight affects offspring’s cardiometabolic profile operates in the prenatal or postnatal period, or both. However, separating the prenatal and postnatal effects is difficult, because maternal overweight exerts its effects in both the prenatal and the postnatal period: many health-related behaviours associated with maternal overweight operate both before and after birth and could, thereby, induce childhood overweight. Meanwhile, study designs have been proposed in which intra-uterine effects might be separated from the postnatal effects. 33 One of those is the comparison of maternal and paternal exposure on the outcome variable. 34,35 If similar associations are found between maternal and paternal exposure, the effect is most likely the result of confounding by shared environmental or genetic factors. 34,35 If, however, the effect of maternal exposure is stronger than paternal exposure, this might hint at intra-uterine effects. Unfortunately, information on paternal pBMI was not available in the ABCD-study. In the literature, results on comparisons of maternal and paternal pBMI point are inconclusive, i.e. some studies found similar associations between maternal/paternal pBMI and birth weight and body composition and cardiometabolic profile at age 6 years, 36-40 whereas others found stronger associations with maternal pBMI than with paternal pBMI. 26,41-43 227 General discussion