Text and Data Mining valid from 2019-11-01
Received: 14 August 2019
Accepted: 18 October 2019
First Online: 1 November 2019
Ethics approval and consent to participate
: This study was approved by the Ethics Committee of the Shanghai First Maternity and Infant Hospital. Date of approving: Jun 13, 2018. Ethical acceptance number: (2018) No. (35).
: Not applicable.
: The authors declare that they have no competing interests.