COVID Vaccination in Pregnant and Lactating Mothers, Transfer of Antibodies to the Baby

While the risk of severe COVID in pregnant women is relatively low, pregnant women with severe COVID experience worse outcomes. Some of our perinatal patients can’t wait to get a COVID-19 vaccine, some of our patients are understandably wary about testing a new vaccine, as there has not been extensive testing of these new vaccines in pregnant and breastfeeding women.  A lot of women simply can’t figure out what is the best thing to do.  

A new study from researchers at Massachusetts General Hospital and Brigham and Women’s Hospital provides some data on the vaccination of pregnant and nursing mothers which hopefully will help women to make informed decisions regarding vaccination if they are pregnant or breastfeeding. The study included 131 women (84 pregnant, 31 lactating and 16 non-pregnant controls), all of whom had received either of the two new mRNA vaccines (Pfizer/BioNTech or Moderna). The preliminary results look good: 

• The new mRNA COVID-19 vaccines appear to be highly effective in stimulating the production of anti-SARS-CoV-2 virus in pregnant and lactating women
• Vaccine-generated antibodies are transferred from the mother to the baby and were detected in all umbilical cord blood and breast milk samples
• Levels of IgG antibodies in the mother were higher in vaccinated women compared to pregnant women who had prior infection with the SARS-CoV-2 virus 

This study provides compelling data to indicate that the Pfizer and Moderna mRNA vaccines generate a robust antibody response in pregnant and lactating women which is similar to what has been observed in non-pregnant adults.  Furthermore, there was no evidence of risk to the baby.

Ruta Nonacs, MD PhD

Gray KJ, Bordt EA, Atyeo C, Elovitz MA, et al.  COVID-19 vaccine response in pregnant and lactating women: a cohort study.  Am J Obstet Gynecol, March 2021.