The Canadian Network of MS Clinics currently recommends that immunization be considered in pregnant and breastfeeding women following a discussion of the potential risks and benefits (https://cnmsc.ca/Covid19VaccineGuidance). This is similar to the WHO recommendation that vaccination be considered in pregnant women at high risk of CoV-2 exposure or with comorbidities (World Health Organization, 29 January 2021. www.who.int/news-room/feature-stories/detail/the-moderna-covid-19-mrna-1273-vaccine-what-you-need-to-know).
Pregnant women are known to have an increased risk of severe COVID-19 illness. The estimated risk of pre-term delivery is 10-25% (Adhikari et al. JAMA Netw Open 2020;3:e2029256). The adjusted risk ratios for COVID-related outcomes in pregnant vs. non-pregnant women are 3.0 for ICU admission, 2.9 for mechanical ventilation, and 1.7 for death (Zambrano et al. MMWR Morb Mortal Wkly Rep 2020;69:1641-1647).
There are limited data on the safety of current COVID vaccines in pregnant women; pregnancy was an exclusion criterion during clinical testing. No safety concerns were raised during animal testing. The U.S. Centers for Disease Control has stated that the current mRNA vaccines are unlikely to pose a specific risk for pregnant women because they do not contain live virus and viral mRNA does not enter host cell nuclei (www.cdc.gov/coronavirus/2019-ncov/vaccines/recommendations/pregnancy.html).
The American College of Obstetricians and Gynecologists recommends that COVID-19 vaccines should not be withheld from pregnant or lactating women (www.acog.org/clinical/clinical-guidance/practice-advisory/articles/2020/12/vaccinating-pregnant-and-lactating-patients-against-covid-19).
The Academy of Breastfeeding Medicine has stated that the lipid nanoparticles in the vaccine would be unlikely to transfer into breast milk; if present, they would be expected to be digested without having a biological effect (www.bfmed.org/abm-statement-considerations-for-covid-19-vaccination-in-lactation).