1. Department of Obstetrics and Gynecology, Lis Maternity Hospital, Tel-Aviv Medical Center, Tel-Aviv, Israel.
2. Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel.
3. Division of Epidemiology, Lis Maternity Hospital, Tel-Aviv Medical Center, Tel-Aviv, Israel.
4. Department of Clinical Microbiology and Infectious Diseases, Hadassah University Hospital, Jerusalem, Israel.