Data Resource Profile: Committee of Nordic Assisted Reproductive Technology and Safety (CoNARTaS) cohort. (19th November 2019) - Opdahl, Signe; Henningsen, Anna-Karina Aaris; Bergh, Christina; Gissler, Mika; Romundstad, Liv Bente; Petzold, Max; Tiitinen, Aila; Wennerholm, Ulla-Britt; Pinborg, Anja B