Maternal Lifestyle and Pregnancy Complications
Adverse maternal lifestyle habits during pregnancy are important modifable risk factors for pregnancy complications in Western countries. Most common adverse maternal lifestyle habits include smoking, alcohol consumption, and caffeine consumption. Although not directly lifestyle related, maternal age is also considered as a modifable risk factor for adverse pregnancy outcomes. Maternal cardiovascular adaptations might be infuenced by this adverse maternal lifestyle during pregnancy, and increase the risks of maternal gestational hypertensive disorders, including pregnancy-induced hypertension and preeclampsia. Maternal age has also been suggested as risk factor for the development of hypertensive disorders during pregnancy. Maternal cardiovascular adaptations might also be involved in pathways leading to an adverse fetal environment and subsequently neonatal complications. As a result of hypertensive complications impaired placental perfusion may occur, and subsequently the oxygen and nutrient supply to the fetus might be limited.
Maternal smoking during pregnancy is a well-established risk factor for various adverse pregnancy outcomes, such as fetal death, preterm birth and fetal growth retardation. Women who smoke during pregnancy have offspring with a lower birth weight of 150 to 200 grams. It has been suggested that the effects of maternal smoking during pregnancy on birth outcomes are trimester specific. High levels of maternal alcohol consumption during pregnancy are associated with birth and long-term developmental defects, fetal alcohol syndrome and increased risks of low birth weight and preterm delivery. Also, previous studies suggested that high caffeine intake during pregnancy is associated with increased risks of miscarriage and fetal death. Similarly, previous studies suggested associations of higher levels of maternal caffeine intake during pregnancy with a lower birth weight. Previous studies suggested an inverse U-shaped relationship between maternal age and birth weight. Whether maternal lifestyle habits explain these associations is not known.
Thus, previous studies showed robust evidence for the associations of high exposures levels of maternal smoking, alcohol consumption and caffeine intake with the risks of perinatal mortality and morbidity. However, less is known about the effects of low to moderate exposure levels on these outcomes. In addition, most previous studies focussed on birth weight as main outcome measure, but birth weight is just a proxy of fetal growth. Different fetal growth characteristics and body proportions might result in the same birth weight. Exposure to adverse maternal lifestyle habits in different trimesters of pregnancy might also have differential effects on fetal growth characteristics. Therefore, studies on exposure effects in different trimesters might identify specifc critical periods. Finally, investigation of factors that may explain the established relationship between maternal age and adverse pregnancy outcomes may help understand the underlying mechanisms. (Figure 1)
The main objectives of the studies presented in this thesis are to examine the associations of maternal lifestyle habits with hypertensive complications during pregnancy, and with fetal growth and the risks of neonatal complications.