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Recent research provides new evidence regarding the safety of COVID-19 vaccinations during pregnancy. The study, presented at the Society for Maternal-Fetal Medicine (SMFM) 2026 Pregnancy Meeting, indicates that receiving an mRNA vaccine while pregnant does not negatively impact a toddler’s brain development. The findings suggest that children born to vaccinated mothers show no difference in reaching developmental milestones compared to those born to unvaccinated mothers.
The question of vaccine safety during pregnancy has been a primary concern for expectant parents since the introduction of COVID-19 immunizations. Messenger RNA, or mRNA, vaccines function by introducing a genetic sequence that instructs the body’s cells to produce a specific protein. This protein triggers the immune system to create antibodies against the virus.
While health organizations have recommended these vaccines to prevent severe maternal illness, data regarding the longer-term effects on infants has been accumulating slowly. Parents often worry that the immune activation in the mother could theoretically alter the delicate process of fetal brain formation.
To address these specific concerns, a team of researchers investigated the neurodevelopmental outcomes of children aged 18 to 30 months. The study was led by George R. Saade from Eastern Virginia Medical School at Old Dominion University and Brenna L. Hughes from Duke University School of Medicine. They conducted this work as part of the Maternal-Fetal Medicine Units Network. This network is a collaboration of research centers funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development.
The researchers designed a prospective observational study. This type of study follows a group of participants over time to observe outcomes rather than intervening or experimenting on them. The team identified women who had received at least one dose of an mRNA SARS-CoV-2 vaccine. To be included in the exposed group, the mothers must have received the vaccine either during their pregnancy or within the 30 days prior to becoming pregnant.
The research team compared these women to a control group of mothers who did not receive the vaccine during that same period. To ensure the comparison was scientifically valid, the researchers used a technique called matching. Each vaccinated mother was paired with an unvaccinated mother who shared key characteristics.
These characteristics included the specific medical site where they delivered the baby and the date of the delivery. They also matched participants based on their insurance status and their race. This matching process is essential in observational research. It helps rule out other variables, such as access to healthcare or socioeconomic status, which could independently influence a child’s development.
The study applied strict exclusion criteria to isolate the effect of the vaccine. The researchers did not include women who delivered their babies before 37 weeks of gestation. This decision was necessary because preterm birth is a known cause of developmental delays. Including premature infants could have obscured the results. The team also excluded multifetal pregnancies, such as twins or triplets, and children born with major congenital malformations.
Ultimately, the study analyzed 217 matched pairs, resulting in a total of 434 children. The primary tool used to measure development was the Ages and Stages Questionnaire, Third Edition, often referred to as the ASQ-3. This is a standardized screening tool widely used in pediatrics. It relies on parents to observe and report their child’s abilities in five distinct developmental areas.
The first area is communication, which looks at how a child understands language and speaks. The second is gross motor skills, involving large movements like walking or jumping. The third is fine motor skills, which involves smaller movements like using fingers to pick up tiny objects. The fourth is problem-solving, and the fifth is personal-social interaction, covering how the child plays and interacts with others.
The researchers analyzed the data by looking for statistical equivalence. They established a specific margin of 10 points on the ASQ-3 scale. If the difference between the average scores of the vaccinated and unvaccinated groups was less than 10 points, the outcomes were considered practically identical.
The results demonstrated that the neurodevelopmental outcomes were indeed equivalent. The median total ASQ-3 score for the vaccinated group was 255. The median score for the unvaccinated group was 260. After adjusting for other factors, the difference was calculated to be -3.4 points. This falls well within the 10-point margin of equivalence, meaning there was no meaningful difference in development between the two groups.
Beyond the general developmental scores, the researchers utilized several secondary screening tools to check for specific conditions. They employed the Modified Checklist for Autism in Toddlers to assess the risk of autism spectrum disorder. The findings showed no statistical difference in risk levels.
Approximately 5 percent of the children in the vaccinated group screened positive for potential autism risk. This was comparable to the 6 percent observed in the unvaccinated group. These percentages suggest that vaccination status did not influence the likelihood of an autism diagnosis.
The team also used the Child Behavior Checklist. This tool evaluates various behavioral and emotional challenges. It looks at internalizing behaviors, such as anxiety, withdrawal, or sadness. It also examines externalizing behaviors, such as aggression or rule-breaking.
The scores for both internalizing and externalizing behaviors were nearly identical between the two groups. For example, 93 percent of children in the vaccinated group fell within the normal range for total behavioral problems. This was the exact same percentage found in the unvaccinated group.
Finally, the researchers assessed temperament using the Early Childhood Behavior Questionnaire. This measures traits such as “surgency,” which relates to positive emotional reactivity and high energy. It also measures “effortful control,” which is the ability to focus attention and inhibit impulses. Across all these psychological domains, the study found no association between maternal vaccination and negative outcomes.
The demographics of the two groups were largely similar due to the matching process. However, one difference remained. Mothers in the vaccinated group were more likely to be nulliparous. This is a medical term indicating that the woman had never given birth before the pregnancy in question.
Additionally, the children in the vaccinated group were slightly younger at the time of the assessment. Their median age was 25.4 months, compared to 25.9 months for the unvaccinated group. The researchers used statistical models to adjust for these slight variations. Even after these adjustments, the conclusion remained that the developmental outcomes were equivalent.
“Neurodevelopment outcomes in children born to mothers who received the COVID-19 vaccine during or shortly before pregnancy did not differ from those born to mothers who did not receive the vaccine,” said Saade.
While the findings are positive, there are context and limitations to consider. The study was observational, meaning it cannot prove causation as definitively as a randomized controlled trial. However, randomized trials are rarely feasible for widely recommended vaccines due to ethical considerations.
Another factor is the reliance on parent-reported data. Tools like the ASQ-3 depend on the accuracy of the parents’ observations, which can introduce some subjectivity. Furthermore, the study followed children only up to 30 months of age. Some subtle neurodevelopmental issues may not manifest until children are older and face the demands of school.
Despite these limitations, the rigorous matching and the use of multiple standardized screening tools provide a high level of confidence in the results for the toddler age group. The study fills a knowledge gap regarding the safety of mRNA technology for the next generation.
“This study, conducted through a rigorous scientific process in an NIH clinical trials network, demonstrates reassuring findings regarding the long-term health of children whose mothers received COVID-19 vaccination during pregnancy,” said Hughes.
The study, “Association Between SARS-CoV-2 Vaccine in Pregnancy and Child Neurodevelopment at 18–30 Months,” was authored by George R. Saade and Brenna L. Hughes, and will be published in the February 2026 issue of PREGNANCY.
