Affiliation: | 1. Division of Obstetrics and Gynaecology, Department of Clinical Science and Education, S?dersjukhuset, Karolinska Institutet, Stockholm, Sweden;2. Division of Obstetrics and Gynecology, Department of Clinical Science, Danderyd Hospital, Karolinska Institutet, Stockholm, Sweden;3. Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden;4. Department of Obstetrics and Gynecology, Asker and Baerum Hospital, Baerum, Norway |