Methods: This study will be performed in a prospective cohort setup (n=200), recruited from the prenatal clinic in the University Hospital Antwerp. The data collection consists of four questionnaires (intake, both urine samples and postpartum), two blood samples (28 weeks and post-partum), two urine samples (20 and 30 weeks), two hair samples (20 weeks and post-partum), cord blood and the placenta.