The study follows 7,050 women who granted permission for follow-up out of the 8,266 pregnant women who filled out a baseline questionnaire at their first prenatal screening. Of those, 7,043 women granted permission for perusal of her and her child’s medical files (85%) and 4,389 women (53%) participated in the biomarker study. The participation rate of Dutch-born women was 77%, and 42-64% for foreign-born women. To enhance participation of foreign-born women, a Turkish, Arabic or English translation was provided to women born in Turkey, Morocco or other non-Dutch speaking countries, and an oral-response interview was offered to women with reading difficulties or who were illiterate.