1 Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, National University Hospital, Singapore; Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
2 Division of Pediatric Infectious Diseases, Department of Pediatrics, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA.
4 Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Division of Infectious Diseases, Department of Medicine, National University Hospital, Singapore.
5 Materno-fetal and Obstetrics Research Unit, Department Woman-Mother-Child, Lausanne University Hospital (CHUV), 1011 Lausanne, Switzerland. Electronic address: david.baud@chuv.ch.