Ronald Gijsen*, Chantal WPM Hukkelhoven, C Maarten A Schipper, Uzor C Ogbu, Mieneke de Bruin-Kooistra and Gert P Westert
* Corresponding author: Ronald Gijsen ronald.gijsen@rivm.nl
BMC Pregnancy and Childbirth 2012, 12:92 doi:10.1186/1471-2393-12-92