Received: 17 May 2020
Accepted: 3 September 2020
First Online: 15 September 2020
Ethics approval and consent to participate
: Ethical approval for this study was granted by the ethics committee of Fujian Provincial Maternity and Children’s Hospital. Permission to access the anonymized (non-identified) data was granted by the Fujian Provincial Maternity and Children’s Hospital Database steering committee.
: All data was anonymized, therefore individual consent for publication was not required.
: The authors declare that they have no competing interests.