1 Department of Obstetrics and Gynecology National Key Discipline, Specialty and Clinical Trial Base, First Affiliated Hospital, Heilongjiang University of Chinese Medicine, Harbin 150040, China.
2 Department of Obstetrics and Gynecology, University of Hong Kong, Hong Kong Special Administrative Region, China.
3 Department of Physiology and Endocrinology, Institute of Neuroscience and Physiology, University of Gothenburg, 40530 Gothenburg, Sweden.
4 Department of Obstetrics and Gynecology National Key Discipline, Specialty and Clinical Trial Base, First Affiliated Hospital, Heilongjiang University of Chinese Medicine, Harbin 150040, China ; Department of Obstetrics and Gynecology and Department of Public Health Sciences, Penn State University College of Medicine, Hershey, PA 17033, USA.