Chong Yap-Seng, Su Lin-Lin
Department of Obstetrics and Gynaecology, Yong Loo Lin School of Medicine, National University of Singapore and National University Hospital, Singapore 119074.
Lancet. 2006 Oct 7;368(9543):1216-8. doi: 10.1016/S0140-6736(06)69497-X.