Strengths and limitations
Our study has several strengths: (1)a population-based single-centered
study, (2) covering a large period between 2013 and 2020, (3) Because
all patients delivered in a medical institution, we have a complete and
systematic review of all medical records. All patients were followed up
6 weeks after delivery and no serious complications were found after
discharge. Also, the study is limited to Shanghai subjects and has
limitations owing to the retrospective design. It only represents the
level of developed regions in China. The situation in other parts of
china is still unknown, so further research is needed to understand the
generalizability of the study findings.