Adriëtte Oostvogels

Methodological considerations This section addresses some methodological issues of this thesis. Maternal prepregnancy BMI In the studies described in this thesis, maternal pBMI was not objectively measured, but relied on women’s self-reported height and weight. These data were collected at around 16weeks of gestation; however, thismay have introduced some bias. Systematic reviews have shown that self-reported BMI in women can be underestimated by up to 2 kg/m 2 compared to conventionally measured BMI. 1,2 Moreover, participants with overweight and obesity tend to underestimate their weight more than participants with normal weight. 3 The possible underestimation of BMI will have weakened the linear associations of the analyses in which pBMI was used as a continuous variable. Moreover, by classifying women as being of normal weight or overweight based on their self-reported BMI, may have led to misclassification. Similar studies have quantified this misclassification as being approximately 14%. 4 This will have led to underestimation of the differences in outcomes between women with overweight and those with normal weight. Therefore, the differences in blood pressure course during pregnancy and postnatal growth between women with overweight and normal weight are likely to be underestimations and, thus, the actual effect might in fact be greater. Maternal early pregnancy lipid profile Results from this thesis show that maternal early pregnancy lipid profile did not mediate the association between pBMI and offspring’s cardiometabolic profile. However, in this thesis, maternal lipid profile was studied in early gestation and not in mid- or late pregnancy. During this time period, foetal weight gain and adipocyte development take place; 5 therefore, this might be a critical window in which maternal lipid profile could influence adipocyte development and, consequently, cardiometabolic profile in childhood. 6-9 Therefore, whether (or not) maternal lipid profile plays a mediating role in the association between maternal prepregnancy weight and offspring’s health later in gestation, remains to be determined. 224 Chapter 9