湖南省自然科学基金面上项目13JJ5012;湖南省科技计划项目2014SK3002;湖南省卫生和计划生育委员会课题B2014-111.Supported by Hunan Provincial Science Foundation13JJ5012;Hunan Provincial Science and Technology Planning Project2014SK3002;Hunan Provincial Health and Family Planning Commision ProjectB2014-111