1. Department of Obstetrics and Gynecology, University of Oulu, Oulu, Finland.
2. Institute of Health Sciences, University of Oulu, Oulu, Finland.
3. Department of Clinical Chemistry, University of Oulu, Oulu, Finland.
4. Department of Children, Young People and Families, National Institute for Health and Welfare, Oulu, Finland.
5. Department of Epidemiology and Biostatistics, Imperial College London, London, United Kingdom.