Analysis of Perinatal Complications and Comorbidities in Hebei Province 
WANG Xiaoxiao,LIU Qing,JIN Ying,ZHANG Yingkui,WANG Li
Chinese General Practice . 2018, (36): 4434 -4438 .  DOI: 10.12114/j.issn.1007-9572.2018.36.004