Funding for this research was provided by:
National Nature Science Foundation of China (81871185, 81961128004)
Health Commmision of Chongqing (2018ZDXM024)
National Nature Science Fundation of China (81520108013, 81771613, 81671488,)
Minisry of Science and Technology (2016YFC1000408)
Received: 5 November 2019
Accepted: 20 March 2020
First Online: 1 May 2020
Ethics approval and consent to participate
: This research was conducted in accordance with the Declaration of Helsinki and approved by the Ethical Committee of Peking University Third Hospital.
: Informed consent was signed by each pregnant participant included in this study.
: The authors declare that they have no competing interests.