November 15, 2024

expert reaction to study on Covid-19 pandemic and heart defects in babies

A study published in Obstetrics and Gynecology looks at heart defects in babies during the Covid-19 pandemic. 

Prof Kevin McConway, Emeritus Professor of Applied Statistics, Open University, said:

“I think this study is best seen as one that can do no more than make a case for more detailed research in the future. I think that the study is statistically sound, as far as it goes, but it has inevitable limitations. The quotations in the press release from Professor Asma Khalil, the lead author, are important. 

“The study is observational, in that the researchers did not intervene in what happened during these pregnancies, but based their conclusions only on what had been observed and recorded. As always in observational studies, it can’t be clear what caused what. It’s possible that the observed increase in the rate of these heart defects, after Covid compared to before, is caused by some effect of SARS-CoV-2 infection, but we can’t be certain that that is what’s going on. And as Professor Khalil points out, even if the virus is somehow causing the increase in the rate of these defects, the study couldn’t give any information on how it might be doing that. There just isn’t the information, in the data sources they used, to tell us. 

“That’s why the study can’t really do more than indicate that the virus might cause an increase in the rate of these particular heart defects. It might not, and if it does, we don’t yet know how that occurs, or indeed how big the increase in risk is.

“Professor Khalil also points out that these are results based on US data, and we don’t yet have results from other parts of the world. The progression on the Covid-19 pandemic and of the responses to it were different in different countries – maybe similar data from other countries would tell a different story, if such data can be obtained.

“In fact, the main statistical analysis, that was the principal basis for the researchers’ conclusions, was rather more subtle than the comparison of numbers of cases per 100,000 live births that is reported in the press release. Those numbers are indeed in the research paper, but they are not adjusted for the factors mentioned in the press release (mother’s BMI, age, some health conditions and so on). These adjustments weren’t used to compare those numbers of cases per 100,000 births. The numbers of cases per 100,000 live births are also not adjusted to allow for the observed fact that the rate of these heart defects was changing over time. Taking those things into account, a more relevant measure is that the increase in the rate of this type of heart defect is around 11% or 12%, a bit less than the 16% quoted in the press release.

“But, whatever the percentage, in absolute terms the increase isn’t very large – mainly because these birth defects are rather uncommon in the USA. Only around 6 in every 10,000 live births are affected. That number would be less than 1 in every 10,000 live births higher a year after the pandemic began, compared to before it. But to know more, we’d need data on (for instance) which of the parents were actually infected or vaccinated, and that couldn’t be done in this research.” 

‘Congenital heart defects during COVID-19 pandemic’ by A. Khalil et al. was published in Ultrasound in Obstetrics and Gynecology at 00:01 UK time on Friday 15th November 2024. 

DOI: 10.1002/uog.29126

Declared interests

Prof Kevin McConway: no conflicts of interest.