Credit CDC
#18,911
We've a large, and highly reassuring study published this week in the JAMA Network, which find no evidence of increased congenital anomalies among pregnant women who received the mRNA COVID vaccine during their first trimester.
These findings mirror those reported by several other smaller studies over the past few years (see HERE, HERE, and HERE).Today's research studied an unusually large sample size (> 527,000), scanning for 75 congenital anomalies, and used robust confounder adjustments. Limitations include: the restriction to live births only, potential residual confounding, and limited power to detect extremely rare defects.
Due to its length, I've just posted the Abstract. Follow the link to read this research report in its entirety. I'll have a brief excerpt after the break.
First-Trimester mRNA COVID-19 Vaccination and Risk of Major Congenital Anomalies
Clément Bernard, MSc1,2; Tom Duchemin, PhD1; Lise Marty, PhD1
JAMA Netw Open
Published Online: October 15, 2025
2025;8;(10):e2538039. doi:10.1001/jamanetworkopen.2025.38039
Key Points
QuestionAre messenger RNA (mRNA)–based COVID-19 vaccines teratogenic ?
Findings In this nationwide cohort study of 527 564 live-born infants, 130 338 (24.7%) were exposed to an mRNA-based COVID-19 vaccine during the first trimester of pregnancy. There was no association with an increased risk for 75 different major congenital malformations, whether examined overall, grouped by organ systems, or individually.
Meaning These findings suggest that mRNA-based COVID-19 vaccines do not appear to have any teratogenic effects.
Abstract
Importance Although messenger RNA (mRNA) COVID-19 vaccines are widely recommended during pregnancy, data on their fetal safety during the teratogenic window remain limited.
Objective To evaluate the association between first-trimester exposure to mRNA COVID-19 vaccines and the risk of major congenital malformations (MCMs), across 75 individual MCMs grouped by 13 organ systems.
Design, Setting, and Participants This nationwide, population-based cohort study was conducted using the comprehensive Mother-Child EPI-MERES Register, including all live-born infants in France from pregnancies starting April 1, 2021, to January 31, 2022. Follow-up data were available up to December 2024.
Exposure Exposure was defined as receiving at least 1 dose of mRNA-based COVID-19 vaccine during the first trimester of pregnancy.
Main Outcomes and Measures MCMs were identified following European Surveillance of Congenital Anomalies guidelines. The main analyses compared exposed and nonexposed infants, and sensitivity analyses used alternative comparison groups based on maternal vaccination status and timing. Confounders were adjusted for using a propensity score–based standardized mortality ratio weighting method. Weighted odds ratios (ORs) were estimated using logistic regression.
Results Among 527 564 eligible live-born infants, 130 338 (24.7%) were exposed to at least 1 vaccine dose during the first trimester. Mothers of exposed infants were slightly older than mothers of unexposed infants (mean [SD] age, 30.4 [5.3] years vs 30.1 [5.1] years), were less socially deprived, and presented slightly more often with a comorbidity. The prevalence of MCMs was 176.6 per 10 000 (2302 infants) among exposed infants and 179.4 per 10 000 (7128 infants) among nonexposed infants. No increased risk of MCMs was observed overall (weighted OR, 0.98 [95% CI, 0.93-1.04]), by organ system (weighted ORs ranging from 0.84 [95% CI, 0.68-1.04] for digestive system MCMs to 1.20 [95% CI, 0.75-1.91] for abdominal wall defects), or for any of the 75 individual MCMs. Sensitivity and stratified analyses confirmed these findings.
Conclusions and Relevance In this cohort study of pregnancies exposed to mRNA COVID-19 vaccines in the first trimester, exposure was not associated with an increased risk of any MCMs, overall, by organ group, or by individual MCM, supporting the safety of mRNA COVID-19 vaccines in early pregnancy.
Over the years we've seen a growing list of studies suggesting a link between viral infections during pregnancy (e.g. Influenza, COVID, RSV, etc.) and a greater risk of congenital defects (see Nature: Severe Influenza in Pregnancy Linked to Neurodevelopmental Disorders in Offspring).
Yet, we continue to see a reluctance among pregnant women - often spurred on by social media - to get the flu and COVID vaccines.
The CDC currently recommends:
Getting a COVID-19 vaccine while pregnant can help protect you and your baby from getting very sick from COVID-19.
If you are pregnant or were recently pregnant, you are more likely to get very sick from COVID-19 than women who are not pregnant. Additionally, if you have COVID-19 during pregnancy, you are more likely to have complications that can affect your pregnancy and developing baby.
COVID-19 vaccination is recommended for everyone ages 6 months and older, including women who are pregnant, breastfeeding, trying to get pregnant now, or who might become pregnant in the future. Evidence shows that COVID-19 vaccination before and during pregnancy is safe and effective and suggests that the benefits of vaccination outweigh any known or potential risks. New data show that vaccination during pregnancy can help protect babies younger than 6 months old, when they are too young to be vaccinated themselves, from hospitalization due to COVID-19.
Everyone, including women who are pregnant, should stay up to date with their COVID-19 vaccines, including getting an updated vaccine when it's time to get one.
Unfortunately, one social media post demonizing mRNA vaccines is apt to get more views than a dozens studies such as today's.
