Adriëtte Oostvogels

1 13 General introduction Although many studies have been performed on the influence of early growth on overweight/obesity in childhood and adulthood, little is known about the role of postnatal growth in the association between maternal overweight and childhood cardiometabolic profile. Animal studies have demonstrated that overnutrition, both pre- and postnatal, is most harmful for offspring’s outcomes. 114-116 For example, offspring from dams on a high-fat diet before and during pregnancy had by far the most detrimental effect on adult body weight and fasting levels of leptin and insulin compared with offspring not exposed to overnutrition, or to postnatal overnutrition alone. 114-116 However, another animal study found that postnatal overnutrition had greater impact on offspring’s metabolism than prenatal overnutrition. 117 There is a lack of evidence on the independent and combined effects of maternal pBMI and postnatal growth on childhood cardiometabolic outcomes as presented in Figure 1. Understanding the role of postnatal growth and the importance of timing of growth in the association between maternal prepregnancy overweight and childhood cardiometabolic profile is important for determining critical periods in early life during which preventive strategies might be most effective. Differences between boys and girls Boys and girls grow differently in utero: boys grow faster than girls and have higher birth weights. 118-121 Postnatally, boys and girls continue to grow differently, 121,122 which is also reflected in separate growth charts for boys and girls applied in Youth Health Care. 2 As boys and girls grow differently in early life, this may result in different responses to early life environmental exposures, 123,124 which might explain sex differences in cardiometabolic disease risks in later life. For example, girls, but not boys, from diabetic mothers were more adipose at the age of 9 years compared to controls. 125 Also differential effects of infant feeding on growth patterns of boys and girls have been previously established: formula fed girls had higher length gain compared to breastfed girls, but no difference was seen in boys. 126 However, studies on sex-specific effects of maternal overweight on childhood cardiometabolic profile, and sex-specific effects of maternal overweight on postnatal growth are lacking. So far, little attention has been paid to sex-specific effects of maternal overweight on childhood cardiometabolic profile. More knowledge on sex differences in response to maternal overnutrition is important in order to prevent sex inequalities in perinatal health care. Professional care givers should keep in mind that maternal overweight/ obesity could have more adverse consequences for either boys or girls and that, for example, crossing a growth chart percentile is more detrimental for one sex than the other. 86