A study published in The Lancet in August 2022 concluded that Covid-19 vaccinations had a “good safety profile” for pregnant people. This was concluded during an attempt to “determine the frequency and nature of significant health events among pregnant females after Covid-19 vaccination”. The “observational cohort study” was conducted across Canada as part of the Canadian National Vaccine Safety (CANVAS) network study.  

The Covid-19 pandemic “disproportionately affected pregnant people” according to the investigators, who explored out higher risks of hospital admission, intensive care unit admission, requirement for ventilation, and death. Furthermore, infection also “increases risk of adverse pregnancy outcomes”, which include impaired foetal growth or preterm birth. In a previous article we explored some of the reasons behind low maternal immunisation rates, suggesting that a lack of data complicated public health communication. Thus, this research is an important step in encouraging pregnant people to come forward when vaccines are available to them.  

Overall, “pregnant vaccinated females had a decreased odds of a significant health event compared with non-pregnant vaccinated females” after both doses of “any mRNA vaccination”. One of the most pressing concerns among pregnant women might be miscarriage or stillbirth, as the most “frequently reported adverse pregnancy outcome”. However, this was “reported at similar rates” between the control group and the vaccinated group. Additional outcomes such as bleeding or reduced foetal movement were “rarely reported” following mRNA vaccination.  

The authors of the study acknowledge the strengths and limitations of their results. One such limitation is that CANVAS is “based on self-reports” and does not feature specific medical verification. This is highly subjective but has been “shown to be reliable for short time periods”. Further limitations can be found in the profile of patient selected, as an email address was required and fluency in French or English was also a prerequisite. 

Despite the handful of limitations, the data provide “reassuring evidence” that mRNA vaccines are “safe in pregnancy”. The study recommends “high vaccine coverage” to protect both pregnant individuals and their infants. Going forward, further research will be required to demonstrate longer-term data.  

Dr Flor Munoz wrote in 2021 that it is “imperative to better understand the potential of immunisation during pregnancy”.* She insisted on data collection to answer the multitude of questions about immunity in pregnancy and beyond. This study is a step in the right direction towards providing the pregnant community with detailed, accurate information on the benefits of receiving vaccines.  

*Dr Flor Munoz-Rivas led the World Vaccine Congress maternal immunity workshop in Washington 2022. To book your place at the congress in 2023 click this link.