1. Department of Obstetrics and Gynecology, School of Medical Sciences , Örebro University , Örebro , Sweden
2. Department of Pediatrics, School of Medical Sciences , Örebro University , Örebro , Sweden
3. Clinical Epidemiology and Biostatistics, School of Medical Sciences, Örebro University , Örebro , Sweden
4. Unit of Biostatistics, Institute of Environmental Medicine, Karolinska Institutet , Stockholm , Sweden
5. University Health Care Research Center, Faculty of Medicine and Health, Örebro University , Örebro , Sweden