OBJECTIVE: The evaluation of the available evidence on vertical transmission by severe acute respiratory syndrome coronavirus 2 (SARS-CoV) -2 .
DATA SOURCES: An electronic search was performed on June 13 , 2020 on the Embase, PubMed and Scopus databases using the following search terms: (Coronavirus OR COVID-19 OR COVID19 OR SARS-CoV-2 OR SARS-CoV2 OR SARSCoV2) AND (vertical OR pregnancy OR fetal). SELECTION OF STUDIES: The electronic search resulted in a total of 2,073 records . Titles and abstracts were reviewed by two authors (WPM, IDESB), who checked for duplicates using the pre-established criteria for screening (studies published in English without limitation regarding the date or the status of the publication). DATA COLLECTION: Data extraction was performed in a standardized way, and the final eligibility was assessed by reading the full text of the articles . We retrieved data regarding the delivery of the potential cases of vertical transmission, as well as the main findings and conclusions of systematic reviews . DATA SYNTHESIS: The 2,073 records were reviewed; 1,000 duplicates and 896 clearly not eligible records were excluded . We evaluated the full text of 177 records, and identified only 9 suspected cases of possible vertical transmission . The only case with sufficient evidence of vertical transmission was reported in France .
CONCLUSION: The risk of vertical transmission by SARS-CoV-2 is probably very low . Despite several thousands of affected pregnant women, we have identified only one case that has fulfilled sufficient criteria to be confirmed as a case of vertical transmission . Well-designed observational studies evaluating large samples are still necessary to determine the risk of vertical transmission depending on the gestational age at infection.