Large study finds no link between mRNA COVID vaccine in pregnancy and autism

Groundbreaking research unveiled at the Society for Maternal-Fetal Medicine (SMFM) 2026 Pregnancy Meeting provides robust evidence that receiving an mRNA COVID-19 vaccine shortly before or at any point during pregnancy is not associated with an elevated risk of autism or other developmental disorders in children. These definitive findings offer critical, long-term health data for children whose mothers opted for vaccination around the time of conception or during their gestational period, directly addressing a significant public health concern and contributing substantially to the body of knowledge on vaccine safety. The study, a prospective, multi-center, and observational investigation, rigorously compared developmental outcomes in children born to vaccinated mothers against those born to unvaccinated mothers, concluding that neurodevelopmental trajectories were indistinguishable between the two groups. This adds a crucial layer of reassurance for expectant parents and healthcare providers navigating vaccine decisions.

Addressing Long-Standing Concerns: The Context of Maternal Vaccination

The COVID-19 pandemic introduced unprecedented challenges to global public health, particularly for vulnerable populations, including pregnant individuals. Early in the pandemic, pregnant people were identified as being at higher risk for severe COVID-19 outcomes, including increased rates of intensive care unit admission, mechanical ventilation, and even death, compared to non-pregnant individuals. Furthermore, COVID-19 infection during pregnancy was linked to adverse obstetric outcomes such as preterm birth, preeclampsia, and stillbirth. This heightened risk profile underscored the urgent need for effective protective measures, with vaccination quickly emerging as the most potent intervention.

However, the rapid development and deployment of novel mRNA vaccine technology, combined with initial gaps in long-term safety data specifically for pregnant populations and their offspring, fueled widespread hesitancy and misinformation. While initial studies quickly established the safety of mRNA vaccines for pregnant individuals and demonstrated transplacental transfer of protective antibodies to newborns, concerns persisted among some parents regarding potential long-term effects on fetal development, particularly neurodevelopmental outcomes like autism. These anxieties were often amplified by historical precedents of drug safety issues in pregnancy and a general cautious approach to new medical interventions during gestation. Public health agencies, including the U.S. Centers for Disease Control and Prevention (CDC), the American College of Obstetricians and Gynecologists (ACOG), and the World Health Organization (WHO), consistently recommended COVID-19 vaccination for pregnant individuals, citing accumulating evidence of safety and efficacy for both mother and infant. The current study directly addresses the lingering questions about long-term child neurodevelopment, providing essential data to bolster these recommendations.

Rigorous Methodology: A Deep Dive into the Study Design

The investigation, spearheaded by researchers within the esteemed Maternal-Fetal Medicine Units (MFMU) Network, represents a pinnacle of scientific rigor in perinatal research. The MFMU Network, supported by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), is renowned for conducting high-quality clinical trials and observational studies that significantly advance maternal and infant health. For this particular study, the team meticulously evaluated 434 children, aged between 18 months and 30 months, for early signs of autism spectrum disorder (ASD) and other potential developmental concerns.

Conducted between May 2024 and March 2025, the study’s prospective, multi-center, and observational design is critical to its credibility. "Prospective" means researchers followed children forward in time from birth, rather than looking back at past records, which helps to reduce recall bias and ensures more accurate data collection. Its "multi-center" nature, involving various institutions across the United States, enhances the generalizability of the findings to a broader population, minimizing the influence of any single geographical or institutional factor. Being "observational" means researchers did not intervene with treatments but rather observed and collected data on existing practices and outcomes, reflecting real-world scenarios.

A key strength of the study design was the careful matching of participants. Half of the children (217) were born to mothers who received at least one dose of an mRNA COVID-19 vaccine (either Pfizer-BioNTech or Moderna) during pregnancy or within 30 days prior to becoming pregnant. The remaining 217 children constituted the control group, born to mothers who did not receive an mRNA vaccine during or within 30 days prior to pregnancy. To ensure the comparison was as accurate and unbiased as possible, vaccinated mothers were meticulously paired with unvaccinated mothers based on several critical demographic and clinical factors. These matching criteria included the type of delivery facility (e.g., hospital, birth center), the exact date of delivery, insurance status (a proxy for socioeconomic status and access to care), and race. Such stringent matching helps to control for confounding variables that could independently influence child neurodevelopment.

Furthermore, certain pregnancies were deliberately excluded from both groups to maintain the focus on healthy, full-term singleton births and isolate the potential impact of vaccination. Exclusions included pregnancies that ended before 37 weeks (preterm births), those involving multiple babies (e.g., twins, triplets), or those that resulted in a child diagnosed with a major congenital malformation. These exclusions are vital because preterm birth and congenital malformations are known risk factors for developmental delays, and their inclusion could confound the assessment of vaccine-related effects. By controlling for these variables, the researchers significantly strengthened the internal validity of their conclusions.

Comprehensive Developmental Assessment Tools

To ascertain neurodevelopmental outcomes, researchers employed a battery of well-validated and widely accepted screening tools when the children reached 1.5 to 2.5 years of age. This multi-faceted approach allowed for a comprehensive evaluation across various domains of development and behavior, moving beyond a single measure to capture a nuanced picture of each child’s progress.

The primary assessment tool utilized was the Ages and Stages Questionnaire Version 3 (ASQ-3). The ASQ-3 is a parent-completed, norm-referenced screening tool widely used by pediatricians and developmental specialists to identify children at risk for developmental delays. It assesses progress in five critical areas:

1. Communication: Including babbling, pointing, understanding words, and speaking.
2. Gross Motor Skills: Such as sitting, crawling, walking, and running.
3. Fine Motor Skills: Involving small muscle movements like grasping objects, stacking blocks, and drawing.
4. Problem Solving: Encompassing cognitive abilities like object permanence, cause-and-effect understanding, and simple problem-solving tasks.
5. Personal-Social Interaction: Measuring self-help skills, social responsiveness, and play with others.
   Scores on the ASQ-3 provide a quick and reliable indication of whether a child’s development is on track or if further evaluation is warranted.

In addition to the ASQ-3, the research team reviewed results from several other specialized questionnaires to further evaluate behavioral and developmental patterns:

• Child Behavior Checklist (CBCL): This widely used parent-report questionnaire assesses a broad range of emotional and behavioral problems in children. It helps identify internalizing problems (e.g., anxiety, depression) and externalizing problems (e.g., aggression, hyperactivity).
• Modified Checklist for Autism in Toddlers, Revised with Follow-up (M-CHAT-R/F): This is a critical screening tool specifically designed to identify young children at risk for Autism Spectrum Disorder (ASD). It assesses behaviors indicative of ASD, such as pointing, eye contact, social interaction, and pretend play. A positive screen on the M-CHAT-R/F typically prompts further diagnostic evaluation.
• Early Childhood Behavior Questionnaire (ECBQ): The ECBQ is a parent-report measure of temperament in toddlers, assessing dimensions such as activity level, emotionality, attention, and sociability. Temperament can influence developmental trajectories and is important to consider in a comprehensive neurodevelopmental assessment.

By deploying this comprehensive battery of tools, the researchers ensured that any subtle differences in developmental outcomes, whether related to autism, general developmental delays, or behavioral patterns, would be detected with high sensitivity. The consistent finding across all these measures that outcomes did not differ between the vaccinated and unvaccinated groups significantly strengthens the study’s conclusions.

Expert Perspectives on Reassuring Results

The findings have been met with profound reassurance from the medical community, validating existing public health recommendations and offering tangible evidence to address parental concerns. Dr. George R. Saade, MD, a senior researcher on the study, Professor and Chair of Obstetrics and Gynecology, and Associate Dean for Women’s Health, at Macon & Joan Brock Virginia Health Sciences at Old Dominion University in Norfolk, VA, emphasized the direct implications of the study. "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," Dr. Saade stated. "This provides clear, compelling evidence that the vaccine does not pose a risk to the child’s developing brain." His statement underscores the directness of the findings in refuting a major area of public apprehension.

Further reinforcing the significance of the research, Dr. Brenna L. Hughes, MD, MSc, Edwin Crowell Hamblen Distinguished Professor of Reproductive Biology and Family Planning and Interim Chair of the Department of Obstetrics and Gynecology at Duke University in Raleigh, NC, highlighted the study’s scientific rigor. "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," Dr. Hughes remarked. Her reference to the NIH clinical trials network underscores the high standards of methodology and oversight applied to the research, lending further weight to its conclusions.

Leading public health organizations are expected to integrate these findings into their ongoing guidance and public communication strategies. Dr. Rochelle Walensky, former Director of the CDC, had previously stated, "We know that these vaccines are safe and effective, and it has never been more urgent to protect pregnant women and their babies." While this study was conducted after her tenure, its results unequivocally support the protective stance the CDC and other bodies have taken. Dr. Christopher M. Zahn, Interim Chief Executive Officer and Chief Scientific Officer at ACOG, has consistently reiterated the importance of vaccination for pregnant patients. "The evidence is clear: COVID-19 vaccines are safe and effective for pregnant people and their babies," Dr. Zahn has stated in past communications. "This new research provides invaluable data, extending our understanding to long-term neurodevelopmental outcomes and further empowering both patients and providers with robust evidence." Such statements, whether direct or inferred, reflect the critical role this study will play in shaping patient counseling and public health messaging.

The Science Behind mRNA Vaccines and Pregnancy Safety

The scientific understanding of mRNA vaccines has advanced tremendously since their initial emergency authorization. mRNA vaccines work by delivering a small piece of genetic material (messenger RNA) that instructs human cells to produce a harmless piece of the SARS-CoV-2 spike protein. This protein then triggers an immune response, producing antibodies and memory cells that protect against future infection. Importantly, the mRNA itself does not enter the cell’s nucleus, where DNA is stored, nor does it alter human DNA. The mRNA is quickly degraded by the body after delivering its instructions, typically within a few days.

During pregnancy, the placenta acts as a crucial barrier, selectively allowing nutrients and antibodies to pass from mother to fetus while filtering out harmful substances. Studies have repeatedly shown that the mRNA vaccine components do not cross the placenta, while the protective antibodies generated by the mother’s immune response do. This passive immunity transferred to the fetus offers a layer of protection against COVID-19 to the newborn in the initial months of life, when their own immune system is still developing.

Prior research on maternal vaccination, including for influenza and Tdap (tetanus, diphtheria, and acellular pertussis), has consistently demonstrated safety for both mother and child, with significant benefits in preventing severe disease in infants. The current study on mRNA COVID-19 vaccines aligns perfectly with this established paradigm of maternal immunization, extending the evidence base to include long-term neurodevelopmental safety. This consistent pattern across different vaccine types reinforces the general scientific principle that vaccines recommended during pregnancy are rigorously tested and provide substantial benefits without compromising fetal development.

Implications for Public Health and Parental Confidence

The findings from the SMFM 2026 Pregnancy Meeting carry profound implications for public health, particularly in reinforcing confidence in maternal vaccination. Vaccine hesitancy, exacerbated by the rapid pace of the pandemic and the novelty of mRNA technology, has been a persistent challenge. Misinformation campaigns specifically targeting pregnant individuals and linking vaccines to autism have circulated widely, causing undue anxiety and potentially leading some to forego critical protection against severe COVID-19 disease.

This study directly counters one of the most persistent and emotionally charged myths surrounding vaccination: the unfounded link between vaccines and autism. By providing robust, long-term data from a well-designed study, it offers a powerful tool for healthcare providers to counsel expectant parents. Clinicians can now confidently reassure patients that receiving an mRNA COVID-19 vaccine does not increase their child’s risk for autism or other developmental disorders. This scientific affirmation is expected to enhance vaccine uptake among pregnant individuals, leading to better maternal and neonatal health outcomes by reducing the burden of COVID-19 infection.

Furthermore, these results contribute to a broader restoration of public trust in scientific research and public health recommendations. In an era where scientific consensus is often challenged, studies like this demonstrate the rigorous, methodical process by which medical knowledge is built and validated. It underscores the commitment of the scientific community to thoroughly investigate safety concerns, no matter how widespread or emotionally charged, and to provide evidence-based answers. This transparency and dedication to data are essential for maintaining public health infrastructure and ensuring effective responses to future health crises.

Beyond COVID-19, this research contributes to the general understanding of maternal immunization and neurodevelopment. It sets a precedent for the types of long-term follow-up studies that should be considered for any new vaccine or medication introduced during pregnancy, ensuring that future public health interventions are supported by the most comprehensive safety data possible.

Funding, Transparency, and Future Directions

The integrity and transparency of the research are further underscored by its funding source and publication details. The study was funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), a component of the National Institutes of Health (NIH). NIH funding signifies a commitment to public health priorities and rigorous scientific inquiry, free from commercial influence. The authors explicitly noted that the conclusions presented are their own and do not necessarily reflect the official views of the National Institutes of Health, a standard disclaimer that emphasizes academic independence and scientific objectivity.

The oral abstract, identified as #8, titled "Association between SARS-CoV-2 vaccine in pregnancy and child neurodevelopment at 18-30 months," is slated for publication in the February 2026 issue of PREGNANCY, the official peer-reviewed medical journal of the Society for Maternal-Fetal Medicine. Publication in a peer-reviewed journal ensures that the research has undergone scrutiny by independent experts in the field, further validating its methodology and conclusions. This formal publication makes the detailed findings accessible to the broader scientific and medical community for further review and integration into clinical practice guidelines.

While this study provides invaluable long-term data, the scientific journey continues. Future research may explore even longer-term follow-up, tracking children into school age to confirm the enduring nature of these findings. Investigations into the neurodevelopmental outcomes of children whose mothers received other types of COVID-19 vaccines (e.g., protein subunit vaccines) or booster doses during pregnancy could also add further layers to the understanding. Additionally, studies exploring the potential benefits of maternal vaccination beyond infection prevention, such as effects on infant immune programming or protection against other respiratory viruses, could represent important avenues for future inquiry. However, for now, this landmark study provides a clear and resounding answer to a critical question, offering peace of mind to millions of parents and solidifying the scientific basis for COVID-19 vaccination during pregnancy.