2.1. Search strategy
The protocol for the meta-analysis was based on the MOOSE checklist(6) (Meta-analysis Of Observational Studies in Epidemiology) and EQUATOR Reporting Guidelines(7) (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). We only conducted a literature review, thus ethics approval was not required.
We systematically searched the literature in PubMed, Web of Science, EMBASE, MEDLINE databases. The retrieval period is from January 1, 2020 to April 16, 2020. The search keywords are ((COVID-19) OR (2019 novel coronavirus infection) OR (COVID19) OR (coronavirus disease 2019) OR (coronavirus disease-19) OR (2019-nCoV disease) OR (2019 novel coronavirus disease) OR (2019-nCoV infection) OR (SARS-CoV-2) OR (Wuhan coronavirus) OR (Wuhan seafood market pneumonia virus) OR (COVID19 virus) OR (COVID-19 virus) OR (coronavirus disease 2019 virus) OR (SARS-CoV-2) OR (SARS2) OR (2019-nCoV) OR (2019 novel coronavirus)) AND ((Pregnancy) OR (Pregnancies) OR (Gestation) OR (Pregnant Women) OR (Pregnant Woman) OR (Woman, Pregnant) OR (Women, Pregnant)). The literature has no language restrictions. We used Endnote X7 library (Clarivate Analytics, Philadelphia, PA, USA) to remove duplicate citations and manage the references. We hand-searched bibliographies of retrieved papers for additional references.