The proportion of babies born with a congenital heart abnormality increased by 16% after the first year of the pandemic, according to research at City St George’s, University of London and published today in Ultrasound in Obstetrics and Gynecology,

Heart defects are the most common type of anomaly that develop before a baby is born, with about 13 babies diagnosed with a congenital heart condition every day in the UK and impacting 1 in 110 births globally. These include defects to the baby’s heart valves, the major blood vessels in and around the heart, and the development of holes in the heart.

In more than 18 million births, researchers analyzed data from US birth certificates from the Center of Disease Control and Prevention (CDC) between December 2016 and November 2022 to evaluate the effect of the pandemic on the number of babies born with a congenital heart defect.

They compared the number of babies born with a congenital heart condition every month before the COVID-19 pandemic (1st December 2016 to 30th November 2019) with those during the pandemic (1st December 2020 to 30th November 2022).

This data was then compared to the number of babies born with Down Syndrome—a genetic condition not affected by the virus. This was to help ascertain if any differences observed might have been due to COVID-19, or if they were a result of other factors including limited access to antenatal services during the pandemic.

A total of 11,010,764 births before and 7,060,626 births during the pandemic were analyzed. Data was adjusted to account for mother’s BMI, diabetes and blood pressure before pregnancy, age, number of times they had given birth and the season in which prenatal care started.

The number of births with a congenital heart condition increased by 16% after the first year of the pandemic, with 65.4 cases per 100,000 live births compared to 56.5 per 100,000 births in the period studied before the pandemic.

The number of babies born with Down Syndrome did not change for the duration of the study, suggesting that the increase in fetal heart defects were not due to a disruption of health services.

Professor Asma Khalil, lead author and professor of obstetrics and maternal fetal medicine at City St George’s, University of London said, “Studying this large US dataset has revealed an unexpected picture for how the pandemic has affected the hearts of unborn babies, but we need to untangle the reasons for this link.

“We need to determine if the SARS-CoV-2 virus directly causes the development of fetal heart problems during pregnancy, and if so, how the virus makes these changes in the heart.

“We don’t have this type of data set available in the UK, but it’s important to see if this pattern is seen in other parts of the world.

“COVID-19 is still circulating and is easier to catch in the winter months. These results act as an important reminder for pregnant women to get their COVID-19 vaccinations to help protect themselves and their baby.”