Chong Yap-Seng, Tan Eng-Kien
Department of Obstetrics and Gynaecology, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore.
Lancet. 2011 Apr 2;377(9772):1127-8. doi: 10.1016/S0140-6736(11)60166-9.