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