COVID-19 vaccine and pregnancy outcomes: a systematic review and meta-analysis

Objectives: To explore perinatal outcomes in SARS-CoV-2 vaccinated pregnant women comparing with unvaccinated counterparts. Methods: Search was conducted using Web of Science, Scopus, ClinicalTrial.gov, MEDLINE, Embase, OVID and Cochrane Library as electronic databases. We included observational studies evaluating pregnant women undergoing SARS-CoV-2 vaccination and compared pregnancy and perinatal outcomes with unvaccinated ones. Categorical variables were assessed using Odds Ratio (OR) with 95% Confidence Interval (CI), while for continuous variables results were expressed as Mean difference (MD) with their 95% Confidence Interval. All analyses were performed by adopting the random effect model of DerSimonian and Laird. Results: There is no difference in the probability of having a small for gestational age fetus (OR 0.97, 95% CI 0.85-1.09; p=0.570), while we observed a reduced probability of a non-reassuring fetal monitoring, a reduced gestational age at delivery and a reduced probability of premature delivery in vaccinated pregnant women versus unvaccinated ones. Conclusion: The probability of small for gestational age is similar between vaccinated and unvaccinated pregnant women, and the former had also a slightly reduced rate of premature delivery. Keywords: COVID-19; SARS-CoV-2; meta-analysis; pregnancy; preterm birth; small for gestational age; systematic review; vaccine.