Contributions to Authorship
The version to be published was approved by all the authors.all authors agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.
Author Jing Wu was responsible for research design and management. Author Qian Liu was responsible for case collection, data analysis, and article writing. Author Xiaomei Shi, Liyuan Fang and Tengzi Rao were responsible for case collection. Author Lishuang Shi was responsible for follow-up work of all cases .
Details of Ethics Aprroval
All pregnant women rolled in the study have given their written informed consent and that the study protocol was approved by the Guangdong Women and Children Hospital Medical Ethics Committee on October 19,2017. The Ethics Review Resolution Number is 20171048.