1. Department of Obstetrics and Gynecology; Princess Margaret Hospital; Hong Kong
2. Prenatal Diagnostic Laboratory; Tsan Yuk Hospital and Department of Obstetrics and Gynecology, Queen Mary Hospital; Hong Kong
3. Department of Obstetrics and Gynecology; Tuen Mun Hospital; Hong Kong
4. Department of Obstetrics and Gynecology; United Christian Hospital; Hong Kong
5. Department of Obstetrics and Gynecology; Queen Elizabeth Hospital; Hong Kong
6. Department of Obstetrics and Gynecology; Pamela Youde Nethersole Easten Hospital; Hong Kong