1 Department of Neonatology, Xingtai People's Hospital Affiliated to Hebei Medical University, Xingtai, Hebei, 054001, China.
2 Department of Obstetrics and Gynecology, Xingtai People's Hospital Affiliated to Hebei Medical University, Xingtai, Hebei, 054001, China.
3 Department of Neonatology, Xingtai People's Hospital Affiliated to Hebei Medical University, Xingtai, Hebei, 054001, China. Electronic address: guowei880923@163.com.