机译:二胎政策实施前后的妊娠和分娩特征分析
Department of Obstetrics and Gynecolog,Peking University Third Hospital,Beijing 100191,China;
Department of Obstetrics and Gynecolog,Peking University Third Hospital,Beijing 100191,China;
Department of Obstetrics and Gynecolog,Peking University Third Hospital,Beijing 100191,China;