Funding for this research was provided by:
Dongguan Social development project (2013108101021;20161081101023)
Received: 29 November 2019
Accepted: 10 May 2020
First Online: 5 June 2020
Ethics approval and consent to participate
: This study was performed with the approval of the Prenatal Diagnosis Center, Dongguan Maternal and Child Health Hospital, Dongguan, and written informed consent was obtained from the patient. The date of approval was 22/03/2018, and the associated reference number was 2018【11】.
: The authors declare that there are no financial or other relationships that might lead to a conflict of interest of the present article. The manuscript is approved by all authors for publication.
: The authors declare that they have no conflict of interest.