1. Department of Development and Regeneration, Cluster Woman and Child, Group Biomedical Sciences, Katholieke Universiteit Leuven, 3000 Leuven, Belgium
2. Institute for the Care of Mother and Child, Third Faculty of Medicine, Charles University, 147 10 Prague, Czech Republic
3. Department of Public Health and Primary Care, Leuven Statistics Research Centre, Katholieke Universiteit Leuven, 3000 Leuven, Belgium
4. Department of Obstetrics and Gynecology, Division Woman and Child, University Hospitals Leuven, 3000 Leuven, Belgium