Researchers wanted to know whether mRNA COVID-19 vaccines given to mothers during pregnancy or within 30 days before conception might affect how babies develop. They studied 434 children in the United States aged 18 to 30 months—half born to vaccinated mothers and half to unvaccinated mothers.
The study took place between May 2024 and March 2025 and was conducted through a major US clinical trials network. To make fair comparisons, the researchers matched vaccinated and unvaccinated mothers by hospital, delivery date, insurance, and race, and excluded pregnancies ending early, multiple births, or babies with major birth defects.
No differences in autism or five key areas of development
When the children turned 18 months to 2½ years old, researchers measured their progress in five developmental areas: communication, large and small muscle movements, problem-solving, and social skills. They also used three separate screening tools to look for autism and behavioural concerns. The vaccinated and unvaccinated groups showed no meaningful differences across any measure.
The study was carefully designed but limited to one country
This research was rigorous—mothers were matched closely on key factors, and children were assessed using validated screening tools. However, the study was conducted only in the United States, and the findings have not yet been published in a peer-reviewed journal (they were presented at a conference in 2026). The sample size, while reasonable, means results should be confirmed by larger studies.
What you can do based on these findings
- If you are pregnant or planning pregnancy, discuss mRNA COVID-19 vaccination with your doctor as an option to protect both you and your baby.
- Use this evidence to ease concerns if you received an mRNA COVID-19 vaccine during pregnancy—developmental outcomes appear comparable to unvaccinated pregnancies.