Pregnant women who receive Pfizer’s coronavirus vaccine are not at increased risk of premature birth or birth defects, according to an Israeli study published Thursday.
The study, published in the journal JAMA Pediatrics and conducted by the Maccabitech Institute for Research and Innovation, analyzed data from 24,288 babies born to women insured by the Maccabi Health Maintenance Organization between March and October 2021. Of these, 16,697 were born to vaccinated mothers while the mothers of the remaining 7,591 were unvaccinated.
Of the vaccinated mothers, 2,134 were vaccinated during the first trimester, a period that is critical to the fetus’ physical development. On average, the researchers monitored the newborns for 152 days after their birth.
“COVID-19 vaccination during pregnancy plays a crucial role in preventing maternal illness,” the researchers wrote in the article’s introduction, explaining their motive for the study. “
Safety concerns are reported as the main reason to decline COVID-19 vaccination during pregnancy. The exclusion of pregnant women from the initial COVID-19 vaccine trials led to information gaps regarding maternal and fetal response to vaccination. While several observational studies examined neonatal benefits via antibody transfer across the placenta, large-scale assessments of neonatal safety are scarce.”
The study compared babies born to vaccinated and unvaccinated mothers based on five parameters – the percentage of premature births, low birth weights, hospitalizations, birth defects and infant mortality – and concluded that there were no significant differences between the two groups. This was true even for the babies whose mothers were vaccinated during the first trimester.
According to the study, 4.2 percent of babies born to vaccinated mothers were born prematurely, compared to 4.8 percent of those born to unvaccinated mothers. Neonatal hospitalization rates were 5.1 percent for the vaccinated and 5.3 percent for the unvaccinated. Birth defects were found in 1.5 percent of the babies with vaccinated mothers and 2.1 percent of those with unvaccinated mothers. The infant mortality rate in both groups was 0.1 percent.
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“The broad sample we took led us to the unequivocal conclusion that there are no differences in the rate of preterm births, low birth weights, hospitalizations, birth defects and infant mortality between mothers who were vaccinated against the coronavirus and those who weren’t vaccinated,” said Dr. Inbal Goldshtein, the study’s lead researcher.
“Vaccination during pregnancy is common to prevent morbidity from other infectious diseases,” the authors noted in their article. “Specifically, vaccines to prevent influenza and pertussis are recommended during pregnancy. The clinical data on safety and efficacy of influenza vaccination are abundant and cover both early and late gestation, as well as longer-term implications into early childhood. However, COVID-19 vaccines were not expressly studied in pregnant women and offspring prior to their availability in the United States under Emergency Use Authorization, leaving an unmet need for safety data.”
The study’s main strengths, the article added, include the fact that “a large, stable cohort of pregnancies linked to offspring” was monitored over time and the “coverage of first trimester exposure.”
Last month, the U.S. Centers for Disease Control and other institutions published a similar study showing that pregnant women vaccinated against the coronavirus had no increased risk of premature birth or low birth weights compared to unvaccinated women.
That study involved 46,079 women, of whom 10,064 had received at least one dose of the vaccine between December 15, 2020 and July 22, 2021 – mainly the Pfizer or Moderna vaccines, and mainly during the second and third trimesters of pregnancy.
That study found higher rates of premature births and low birth weights than the Israeli study did (6.6 and 8.2 percent, respectively), but no significant differences between the vaccinated and unvaccinated groups.