1 Department of Obstetrics and Gynaecology, National University Hospital, Singapore.
2 Department of Obstetrics and Gynaecology, National University Hospital, and Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
3 Division of Respiratory and Critical Care Medicine, National University Hospital, and Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
4 Division of Infectious Diseases, National University Hospital, and Yong Loo Lin School of Medicine, National University of Singapore, Singapore.