COVID vaccination in pregnancy showed no effect on toddlers' neurodevelopment

One of the most persistent worries aired about COVID-19 vaccination in pregnancy was never about the mother. It was about the child: whether a shot given while the brain was forming might, years later, show up as a developmental difference. A multicentre US study published on 2 November in JAMA Pediatrics addresses that question directly, and the answer is reassuring [s1].

What the study did

Researchers from the Eunice Kennedy Shriver National Institute of Child Health and Human Development's Maternal-Fetal Medicine Units Network ran a prospective cohort study across 14 centres, assessing children aged 18 to 30 months between 2024 and 2025 [s1]. The design hinged on careful matching. Women who had received a SARS-CoV-2 mRNA vaccine during pregnancy, or within 30 days before it, were paired with women who had not, matched on delivery site, delivery date, insurance status, and race and ethnicity [s1]. Matching on exposures that otherwise track with both vaccination and child development is how an observational study tries to isolate the thing it is actually testing.

Of 3,956 women screened, 271 vaccinated (exposed) and 240 unvaccinated (unexposed) children were enrolled, and full matching was possible for 217 pairs — 434 children in the analysis [s1]. The group was 258 (59.4%) Non-Hispanic White, 96 (22.1%) Non-Hispanic Black, 52 (12.0%) Hispanic and 28 (6.5%) of other backgrounds [s1]. Median age at assessment was 25.8 months, and the sample was almost evenly split, 221 female (50.9%) and 213 male (49.1%) [s1].

The primary outcome was the Ages and Stages Questionnaire, third edition (ASQ-3), a widely used developmental screen scored by parents. The team set an equivalence test in advance: the two groups would be judged equivalent if the 90% confidence interval for the median difference fell between −10 and 10 points [s1]. Setting that boundary before seeing the data matters — it commits the researchers to a definition of "no meaningful difference" rather than letting a null result be declared after the fact.

What it found

The groups were equivalent. Median ASQ-3 total scores were 255 in the exposed children and 260 in the unexposed, an adjusted median difference of −3.4 with a 90% confidence interval of −9.8 to 3.0 [s1]. That interval sits entirely inside the prespecified margin, so the result is not merely a failure to find a difference; it is positive evidence that any difference is too small to matter developmentally.

The secondary outcomes pointed the same way. Domain-specific ASQ-3 scores, the Child Behavior Checklist, the Modified Checklist for Autism in Toddlers and the Early Childhood Behavior Questionnaire showed no significant differences between the groups [s1]. The inclusion of an autism screen is notable, given how often that specific fear has attached to vaccination. Nothing in these measures separated the children whose mothers were vaccinated from those whose mothers were not.

How to read it

Several limits are worth naming. This is an observational cohort, not a randomised trial, so matching reduces but cannot entirely remove confounding — vaccinated and unvaccinated mothers may still differ in ways the four matching variables did not capture. The exposed mothers were more often first-time mothers, and their children were slightly younger at assessment and more likely to have been vaccinated themselves [s1]. The sample is also modest, 217 pairs, and the ASQ-3 is a screening instrument reported by parents rather than a formal diagnostic assessment. These are reasons to read the result as strong reassurance rather than a final verdict, particularly for rarer outcomes a study this size cannot rule in or out.

The finding also belongs beside a related but distinct question: the effect of COVID infection, not vaccination, in pregnancy. A large Norwegian cohort published in September found no broad raised risk of autism or most neurodevelopmental disorders after maternal COVID infection [s2]. The two studies examine opposite exposures — catching the virus versus being vaccinated against it — but together they map the same reassuring territory from both directions.

For a pregnant woman weighing the COVID vaccine, the practical message is narrow and clear. On the outcome parents most often ask about — how the child turns out — this study found no signal, and its authors conclude the findings support continued recommendations for mRNA COVID vaccination in pregnancy [s1]. That recommendation already rested on protection for the mother and newborn against severe COVID; what this adds is direct evidence on the long-range worry that protection might carry a developmental cost. It does not. This article is informational and is not medical advice.