1. Department of Obstetrics and Gynaecology, the First Affiliated Hospital of Kunming Medical University, PO Box 650032, No.295 Xi Chang Rd, Kunming, Yunnan Province, China.
2. Department of Obstetrics and Gynaecology, Chinese University of Hong Kong, Hong Kong Special Administrative Region, China.
3. Department of Paediatrics, First Affiliated Hospital of Kunming Medical University, Kunming, China.