This thesis aims to reveal pathways underlying the associations of air polluion exposure during pregnancy with maternal and neonatal complications. The main objectives were:
1.  To examine the associations of air pollution exposure during pregnancy with the risks of gestational hypertensive complications and neonatal complications.
2.  To examine the mechanisms that underlie the associations of air pollution exposure during pregnancy with maternal and neonatal complications. Mechanisms of interest are placental function, in?ammatory responses, maternal blood pressure, and fetal growth.

All studies described in this thesis were embedded in the Generation R Study, a population based prospective cohort study from pregnancy onward in Rotterdam, the Netherlands. The Generation R Study was designd to identify early environmental and genetic determinants of growth, development, and health during fetal life and childhood. All pregnant women living in the study area with a delivery date between April 2002 and January 2006 were eligible for enrolment in the study. The aim was to enrol participants during pregnancy, but enrolment was allowed until the birth of the child. In total, 9778 women were included, of whom 8880 were enrolled in the prenatal part of the study. The largest ethnic groups were the Dutch, Surinamese, Turkish, and Moroccan. Data on pregnancy were collected on the basis of questionnaires, physical examinations, fetal ultrasound examinations, biological samples, and medical records completed by midwives and obstetricians. Physical assessments were performed in early pregnancy (gestational age <18 weeks), mid-pregnancy (gestational age 18-25 weeks), and late pregnancy (gestational age ≥25 weeks), but the individual time schemes depended on the speci?c gestational age at enrolment. Postnatal data was obtained by community health centers and questionnaires. From the age of 5 years onward, regular detailed hands on assessments are performed in all children and their parents in a research center. The Generation R study has been approved by the Medical Ethical Committee of the Erasmus Medical Center Rotterdam. All participants provided written informed consent.