Received: 30 June 2018
Accepted: 12 November 2018
First Online: 20 December 2018
Ethics approval and consent to participate
: This study has been approved by the ethics committee of the First Affiliated Hospital of Zhengzhou University, the Third Affiliated Hospital of Zhengzhou University, and Jiangxi Provincial Maternal and Child Health Hospital. It will abide by the relevant laws and regulations on drug testing ethics. All patients will sign the informed consent for the study protocol and reserve the right to withdraw at any time. The archives of the pregnant patients will be kept for over 50 years according to the requirement of clinical trials.
: Not applicable.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.