1. Perinatal Center; Department of Obstetrics and Gynecology; Sahlgrenska University Hospital/Östra; Institute for Clinical Sciences; Sahlgrenska Academy at the University of Gothenburg; Gothenburg Sweden
2. Department of Pediatrics; Institute for Clinical Sciences; Sahlgrenska Academy at the University of Gothenburg; Gothenburg Sweden
3. Department of Mathematical Statistics; Chalmers University of Technology; Gothenburg Sweden
4. Department of Genes and Environment; Division of Epidemiology; Institute of Public Health; Oslo Norway