Two recent studies from Europe show mRNA COVID-19 vaccines were not linked to birth defects if administered in the first trimester, nor were they associated with perceived increases in adverse effects.
In the first study, published in Clinical Microbiology and Infection, German researchers compared congenital birth defects among 1,828 pregnant women who were vaccinated with an mRNA vaccine in the first trimester (before 13 weeks' gestation), and 1,955 pregnant women who were not vaccinated.
All information on outcomes and participants came from the German Embryotox Centre of Clinical Teratology and Drug Safety in Pregnancy, a national center that provides advice and risk assessment on drug use in pregnancy.
In total, 68 major congenital malformations were observed in the vaccinated and 53 in the unexposed cohort (3.9% vs 3.1%). The adjusted odds ratio for major birth defects in the exposed group was 1.30 (95% confidence interval, 0.90 to 1.86).
Our study results showed no statistically significant increase in the overall rate of major birth defects after maternal vaccination with mRNA COVID-19 vaccine in the first trimester.
All analyses were statistically not significant, the authors wrote: “Our study results showed no statistically significant increase in the overall rate of major birth defects after maternal vaccination with mRNA COVID-19 vaccine in the first trimester. This is consistent with the results of other research groups."
Findings are reassuring
In a second study published in Birth Defects Research, Dutch researchers compared adverse events (AEs) after maternal vaccination with COVID-19 mRNA vaccines and determined whether rates were comparable to those in non-pregnant populations.
Overall, both pregnant and non-pregnant women were captured in the Dutch Pregnancy Drug Register and the cohort event monitoring study on COVID-19 vaccines.
The pattern of AEs was similar between pregnant (2,204) and non-pregnant (2,684) women, the authors found. The four most frequently reported AEs were injection site reactions, myalgia (muscle pain), fatigue, and headache.
Pregnant women were less likely to report at least one AE than non-pregnant women (65.9% vs 72.3%). They were also less likely to report nausea, chills, fever, and joint pain.
“Possible explanations for the differences in perceived AEs between pregnant and nonpregnant women are the immunological, hormonal, and physiological changes during pregnancy,” the authors wrote. “For example, immunological adaptations could possibly lead to less reactogenicity after vaccination.
“These results, together with previous safety and effectiveness studies, are reassuring for the current advice to vaccinate pregnant women against COVID-19 and for the safety of maternal vaccination in general,” they concluded.
