The prevalence of congenital heart disease (CHD) among in vitro fertilization (IVF) pregnancies was similar to that of the general population, but there is an increasing risk of CHD among twins resulting from IVF, according to research by Yale School of Medicine researchers.

Mert Ozan Bahtiyar, M.D., assistant professor in the Department of Obstetrics, Gynecology & Reproductive Sciences, will present the abstract on January 31 at the Society for Maternal-Fetal Medicine Annual Meeting in Dallas, Texas.

Working with the Fetal Cardiovascular Center at Yale University and Yale-New Haven Hospital, a central referral center for the State of Connecticut, Bahtiyar and his colleagues examined almost 2,000 patients using fetal echocardiography. The study lasted from January 1, 2006 through July 31, 2007. Among those patients, 250 women were specifically seen due to pregnancy resulting from in vitro fertilization. They did not have other medical problems that would require echocardiograms. The team conducted 357 fetal echocardiograms for 347 fetuses on these 250 women. Approximately 30 percent had twin pregnancies.

“We found that twin pregnancies conceived through IVF have a higher prevalence of CHD than singletons,” said Bahtiyar, who saw a three-fold increase. “IVF twins are usually fraternal, but past studies of identical twins also showed up to a 13-fold increase in congenital heart defects.”

Bahtiyar said that previous reports of increased CHD risk in pregnancies conceived via IVF may be due, in part, to a higher frequency of multiple pregnancies resulting from this form of conception. “The increased twinning seems to be the cause of the abnormality and not IVF per se.”

Bahtiyar and his team plan to increase the number of study subjects to replicate these preliminary results.

“The next step is to explore why this is happening,” he said. “Knowing about the risk of these defects will help increase the likelihood of survival after birth.”

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Other authors on the study included Antonette T. Dulay, Bevin P. Weeks, Alan H. Friedman and Joshua A. Copel.

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