重庆市科学技术委员会科技攻关项目CSTC2013ggB0012;重庆市人口和计划生育科学技术研究院基本科研业务费项目1207Supported by the Science and Technology research project of Chongqing Science and Technology Commission CSTC2013ggB00001;Fundamental Research Project of Population and Family Planning Science and Technology Institute 1207