You can’t blame this one on the stork.
After a brief baby bump early in the COVID-19 pandemic, birth rates in the US and other wealthy countries dropped as the public health emergency eased.
That sudden decline sparked online speculation that the rollout of mRNA COVID-19 vaccines could have played a role, with critics suggesting the shots may have hurt fertility or made it harder to carry a pregnancy to term.
To test those claims, researchers in Sweden — a nation that also saw births fall later in the pandemic — decided to dig into the data.
They analyzed health information from nearly 60,000 women ages 18 to 45 living in Region Jönköping County in southern Sweden.
About 75% of the women were vaccinated against COVID-19 between 2021 and 2024, and 97% of those shots were mRNA vaccines.
When the researchers compared childbirth rates between vaccinated and unvaccinated women, they found no statistically significant difference between the two groups.
“We’ve also looked at all registered miscarriages among those who became pregnant, and we see no difference between the groups there either,” Toomas Timpka, professor of social medicine at Linköping University and one of the study authors, said in a statement.
“Our conclusion is that it’s highly unlikely that the mRNA vaccine against COVID-19 was behind the decrease in childbirth during the pandemic,” he continued.
The findings align with previous large-scale studies and reviews involving hundreds of thousands of pregnant women, which have found no evidence that COVID vaccines increase the risk of miscarriage or stillbirth.
Major medical organizations, including the American College of Obstetricians and Gynecologists (ACOG), have likewise reported that research has found no impact of COVID vaccines on male or female fertility.
“This should further reassure women that COVID vaccination will not prevent them from getting pregnant or having a baby,” Dr. Viki Male, an an associate professor in reproductive immunology at Imperial College London, who was not involved in the study, said in an interview with the Center for Infectious Disease Research and Policy at the University of Minnesota.
Still, it’s true that birth rates have fluctuated since the pandemic began.
Births in most high-income countries dipped early in the outbreak and briefly rebounded in 2021, but research shows they began falling again by early 2022.
In the US, the decline hit a record low in 2024, when the fertility rate dropped to less than 1.6 kids per woman, according to the CDC.
But the researchers say there are “alternative and more plausible explanations” for the drop, including concerns about health, job uncertainty, inflation and behavior changes tied to lockdowns.
Plus, the general fertility rate in the US was already at an all-time low before the COVID-19 pandemic began, which suggests the decline wasn’t driven by a single factor.
While the study found no evidence linking vaccination to fewer births, contracting COVID during pregnancy poses real risks for mom and baby.
Studies show pregnant and recently pregnant women face a higher risk of severe illness or death from the virus than women who are not pregnant.
Infection while carrying a child has also been linked to pregnancy complications such as life-threatening hypertension, preeclampsia, preterm birth and stillbirth.
By contrast, research shows pregnant women who contract COVID after being vaccinated are far less likely to be hospitalized, require intensive care or deliver prematurely than unvaccinated women.
There may also be long-term effects on children.
Scientists have found that children born to mothers who had COVID while pregnant face an increased risk of developmental disorders by age 3, including speech delays, autism and motor disorders.
Some evidence also suggests their immune systems may be weakened after exposure in the womb.
Health experts say vaccination remains the strongest protection against severe COVID illness, hospitalization and death.
Yet federal guidance has shifted. Last year, the Trump administration removed the COVID vaccine from the list of shots recommended for healthy pregnant women and children.
The CDC now advises that people considering vaccination engage in “shared clinical decision-making” with a doctor, nurse or pharmacist.
Major medical groups, including ACOG and the Society for Maternal-Fetal Medicine, continue to recommend COVID vaccination for pregnant and breastfeeding women.
