1. School of Nursing, The Hong Kong Polytechnic University, Hong Kong, China.
2. Hospital of Chengdu University of Traditional Chinese Medicine, Chengdu, China.
3. Reproductive &Women-Children Hospital, Chengdu University of Traditional Chinese Medicine, Chengdu, China.
4. School of Medical and Life Sciences, Chengdu University of Traditional Chinese Medicine, Chengdu, China.
5. Sichuan Family Planning Research Institute, World Health Organization Collaborating Centre (WHOCC), Chengdu, China.