Covid-19: two studies reassure on vaccination during pregnancy

Messenger RNA anti-Covid vaccines pose little risk in pregnant women according to two recent studies, one of which shows in particular that there is no particular danger of miscarriage or premature birth.

The first, published last week in the Lancet Infectious Diseases, assesses the immediate risks of side effects in pregnant women after a messenger RNA vaccine.

The second, published Thursday in the British Medical Journal (BMJ) measures, in the longer term, the risks in childbirth.

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Both studies present reassuring conclusions about these vaccines, one developed by Pfizer/BioNTech and the other by Moderna, which are at the heart of anti-Covid vaccination in several countries such as France.

"Anti-Covid-19 vaccination during pregnancy is not associated with a higher risk of preterm birth (or) miscarriage", summarize the authors of the BMJ, also concluding that there is no danger that the newborn is abnormally small.

This work, conducted in Canada, retrospectively studied more than 85,000 births or miscarriages that occurred between May and December 2021. In about half of the cases, the mother had received one or two doses of the Covid vaccine - mostly to messenger RNA - during her pregnancy.

Ultimately, pregnancy outcome is not different in this group.

5,000 women vaccinated during pregnancy were monitored

As for the immediate side effects of messenger RNA vaccines, they are generally not more frequent during pregnancy, according to the Lancet Infectious Diseases study.

The authors compared the data of more than 5,000 women vaccinated during their pregnancy with those of some 300 pregnant and unvaccinated women.

They measured the proportion of "significant" health problems - which require interrupting one's professional activity or consulting a doctor - in the week following vaccination, in the first group, or in the week preceding the answer to their questionnaire, in the second.

No difference is seen after the Pfizer/BioNTech vaccine, or the first dose of Moderna.

On the other hand, after the second dose of it, the risk increases a little.

However, even after a second dose of Moderna, there is no difference if only the conditions requiring a medical consultation are taken into account.

"Messenger RNA vaccines against Covid 19 have a good safety profile during pregnancy", conclude the authors.