Study highlights the safety profile of mRNA COVID-19 vaccines during pregnancy

By Dr. Sanchari Sinha Dutta, Ph.D.Aug 15 2022Reviewed by Aimee Molineux

The British Medical Journal has recently published an article describing that mRNA-based coronavirus disease 2019 (COVID-19) vaccines are safe during pregnancy. The conclusion has been made based on the available evidence from large-scale studies.

Pregnancy adversities caused by COVID-19  

The COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has adversely affected pregnant women who are at higher risk of severe disease. Increased rates of hospitalization, intensive medical care, mechanical ventilation, and even death have been observed among pregnant women compared to that among non-pregnant women.

The most commonly observed COVID-19-related pregnancy adversities include hypertension, pre-eclampsia, impaired fetal growth, and preterm birth.

Pregnancy and COVID-19 vaccination

A gradual increase in the vaccination rate has been observed among pregnant women during the COVID-19 pandemic. However, the proportion of vaccinated pregnant women is still low in the general population. The lowest vaccine uptake has been observed among pregnant women who live in socioeconomically-deprived regions.

Several observational studies have been done throughout the COVID-19 pandemic to evaluate the safety, reactogenicity, and tolerability of COVID-19 vaccines in pregnant women. The majority of these studies have highlighted that the vaccines are safe for use during pregnancy.  

A recent study conducted in seven Canadian provinces and territories has concluded that pregnant women experience lower rates of adversities after COVID-19 vaccination compared to non-pregnant women.

The Canadian study was conducted on a total of 5625 pregnant and 185,735 non-pregnant women who had received either the first dose or second dose of mRNA-based COVID-19 vaccines (Pfizer and Moderna). In addition, 339 pregnant women who did not receive COVID-19 vaccination were included as age-matched controls. Self-reported information on vaccination-related adversities was collected from the participants within seven days after each vaccine dose.

Overall, the study findings revealed that about 4% and 7% of pregnant women experienced significant health adversities after the first and second vaccine dose, respectively. In contrast, about 11% of vaccinated non-pregnant women experienced significant health adversities after the second vaccine.

About 3% of pregnant unvaccinated women experienced significant health adversities in the previous week. This observation indicates that all adversities experienced by vaccinated pregnant women might not be related to vaccination; some of these adversities could be related to pregnancy in general.  

The most common health adversities included feelings of being unwell, headaches, and respiratory tract infections. Among all participants, less than 1% experienced serious health adversities that require hospitalization or emergency department visit. Regarding adverse pregnancy outcomes, about 1.4% and 2.1% of vaccinated and unvaccinated pregnant women reported miscarriage and stillbirth, respectively.

As mentioned by the scientists, the study has limitations. Most study participants are White women, and thus, the findings might not be generalized to other ethnicities. In addition, the study has reported health adversities that occurred within seven days after vaccination and thus, cannot explain any long-term consequences that might occur after COVID-19 vaccination.     

Conclusion

The BMJ article explains the safety profile of mRNA COVID-19 vaccines during pregnancy. Based on the available evidence, the article indicates that pregnant women should consider receiving COVID-19 vaccination to avoid negative health consequences associated with SARS-CoV-2 infection.

Given the low vaccine uptake among pregnant women, Sascha Ellington and Christine Olson, from the US Centers for Disease Control and Prevention (CDC), mention that,

It is imperative that we continue to collect and disseminate data on the safety and effectiveness of covid-19 vaccination in pregnancy and to encourage healthcare providers to promote vaccination during all trimesters of pregnancy.”