Adriëtte Oostvogels

2 35 pBMI, lipids and BP during pregnancy Introduction Overweight or obesity before pregnancy is associated with hypertensive disorders of pregnancy, 1, 2 which in turn are associated with maternal, foetal and infant mortality. 3,4 Therefore, identifying modifiable risk factors affecting the blood pressure (BP) course in pregnancy is important as they may be instrumental in devising new preventive and therapeutic strategies. Women with overweight or obesity display a different BP course than women with normal weight. 5-7 Normally, blood pressure decreases from the start of pregnancy under the influence of progesterone and prostaglandins, and due to increased uteroplacental circulation, 8 reaching a nadir in midpregnancy. 9 From here BP increases to normal prepregnancy blood pressure at term 9 as blood volume increases to compensate for the increased uteroplacental circulation and for blood loss at delivery. 8 Compared to women with normal weight, women with overweight or obesity start their pregnancy with a higher BP, have a smaller BP decrease to midpregnancy and a faster increase until the end of pregnancy. 5,6 Women with overweight or obesity also have a more atherogenic lipid profile throughout pregnancy. 10-12 A more atherogenic lipid profile in pregnancy is associated with hypertensive disorders of pregnancy, independent of maternal weight status. 13-17 The lipid profile changes during pregnancy: in early pregnancy lipids are low and an accumulation of maternal fat depots is followed by increased adipose tissue lipolysis and subsequent hyperlipidaemia in late pregnancy. 11,12 At this stage, triglyceride-rich particles and related remnants can damage the endothelium through lipid-mediated oxidative stress mechanisms, 18,19 leading to higher BP. 20 Although associations between a more atherogenic lipid profile and hypertensive disorders of pregnancy have been reported, the association between early pregnancy lipid profile and BP course, especially in the first half of pregnancy, remains unknown. To our knowledge, the role of both prepregnancy weight status and early pregnancy lipid profile on BP course during pregnancy has not yet been studied. Therefore, this study aimed to describe the association between prepregnancy weight status and BP course and the role of early pregnancy lipid profile: i.e. does the lipid profile mediate or moderate this association? The present study used data from the large Dutch prospective ABCD study to examine these associations. Based on the literature, we hypothesise that women with overweight, partly due to their more atherogenic lipid profile, start their pregnancy with a higher BP and have a smaller decrease in BP in the first half of the pregnancy, but a greater increase in the second half of the pregnancy (mediation). Moreover, we expect to find the most detrimental outcomes (i.e. the highest absolute BP with the steepest increase in BP during pregnancy) in women with overweight with a more atherogenic lipid profile (moderation).