Article History
Received: 4 June 2021
Accepted: 17 December 2021
First Online: 6 January 2022
Declarations
:
: This study was conducted in accordance with the Declaration of Helsinki and was approved by the Ethical Committee of the Peking University Third Hospital (number M2016199, on March 8, 2017). Each monochorionic placenta diagnosed prenatally with ultrasound was examined after delivery pathologically and by dye injection with the approval of Ethics Committee of Peking University Third Hospital and the informed consent of patients.
: All authors agree to publish the article in this publication.
: The authors declare that they have no competing interests.