COVID-19 Disease and Vaccination in Pregnant and Breastfeeding Women

Reviewed by Michael Payne, MD, London Health Sciences Centre and Erica Stohs, MD, MPH, University of Nebraska Medical Center

Meta-analyses analyzing pregnancy outcomes from COVID-19 disease and the safety of COVID-19 vaccination during pregnancy are newly available. Additionally, a research brief examines SARS-CoV-2 specific antibodies in breastmilk following vaccination in breastfeeding women.

A systematic review and meta-analysis of observational studies investigating the impact of SARS-CoV-2 infection during pregnancy on associated outcomes. COVID-19 infections were stratified by disease severity. The meta-analysis included 42 studies involving 438,548 pregnant persons. Compared with no infection in pregnancy, COVID-19 was associated with preeclampsia (OR 1.33), preterm birth (OR 1.82) and stillbirth (OR 2.11). Compared with mild COVID-19, severe COVID-19 was strongly associated with preeclampsia (OR 4.16), preterm birth (OR 4.29), gestational diabetes (OR 1.99) and low birth weight (OR 1.89). This study further clarifies the impact of COVID-19 infection on pregnancy outcomes, with severe COVID in particular as a risk factor for preterm labor and preeclampsia. 

Next, data from the CDC’s “V-safe after vaccination health checker” surveillance system, the V-safe pregnancy registry, and the Vaccine Adverse Event Reporting System (VAERS) from mid-December to the end of February examined safety data from pregnant persons receiving mRNA COVID-19 vaccines. There were over 40,000 pregnant participants in the first 2 registries and 221 pregnancy-related adverse events reported in VAERS. Injection-site pain was reported more frequently in pregnant vs non-pregnant women, while headache, myalgias, chills and fever were less frequently reported in pregnancy. Pregnancy outcomes are forthcoming but among 3958 participants in the v-safe pregnancy registry, about 20% have completed pregnancy with 14% resulting in pregnancy loss and 86% resulting in live birth. Adverse neonatal outcomes included pre-term birth (9.4%), small for gestational age (3.2%); no neonatal deaths were reported. Based on published incidences before the pandemic, adverse pregnancy and neonatal outcomes among vaccinated persons with completed pregnancies do not show any obvious safety signals or concerns.

Last, a small prospective cohort study examined passive immunity from COVID-19 vaccination by quantifying SARS-CoV-2-specific IgA and IgG in frozen weekly breastmilk samples from 84 breastfeeding women immunized with Pfizer-BioNTech vaccine spaced 21 days apart. IgA was significantly elevated 2 weeks after the initial vaccine, peaked by week 4 and remained elevated at week 6 when sampling ended. IgG increased at week 4 after initial vaccination and remained detectable in 97% of samples at week 6. The implication of these results suggests potential protective effect against infection in breastfeeding infants, but the duration of protection has yet to be seen. 


  • Shu Qin Wei, Marianne Bilodeau-Bertrand, Shiliang Liu and Nathalie Auger. The impact of COVID-19 on pregnancy outcomes: a systematic review and meta-analysis. CMAJ April 19, 2021 193 (16) E540-E548; DOI:
  • Shimabukuro TT, et al. Preliminary findings of mRNA COVID-19 vaccine safety in pregnant persons. NEJM. Published online April 21, 2021. DOI: 10.1056/NEJMoa2104983
  • Perl SH, et al. SARS-CoV-2-specific antibodies in breast mild after COVID-19 vaccination of breastfeeding women. JAMA. Published online April 12, 2021. DOI: 10.1001/jama.2021.5782
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