NEW YORK, Sept 28: In a significant study published on Thursday, researchers have found that major heart defects are more prevalent—though still rare—among babies conceived via certain fertility treatments, including in vitro fertilization (IVF). This research is the largest of its kind, encompassing medical records from over seven million Nordic children.

The study, which analyzed children born between 1984 and 2015 in Denmark, Sweden, Norway, and Finland, highlighted that assisted reproductive technology (ART), predominantly IVF, is linked to a small yet notable increase in birth abnormalities. “It’s an increased risk, but the absolute risk is very small,” stated Dr. Ulla-Britt Wennerholm, the senior author and a professor of obstetrics and gynecology at the University of Gothenburg in Sweden. She added, “I think that’s a reassuring finding, actually.”

According to the findings, the risk of a major heart defect was approximately 36 percent higher in children conceived through ART compared to those conceived naturally. Nevertheless, these defects remain uncommon, with less than 2 percent of infants born through ART experiencing major heart defects. The research also revealed that the likelihood of heart defects did not vary based on whether the parents underwent intracytoplasmic sperm injection (ICSI) or IVF, nor did it differ if the implanted embryos had been frozen or transferred shortly after fertilization.

The established connection between IVF and various birth defects—affecting muscles, genitals, and the gastrointestinal tract—has been noted in existing scientific literature. However, the specific reasons for this association remain unclear. One hypothesis suggests that aspects of the IVF process—such as extracting eggs and fertilizing them in a laboratory—may play a role. Another theory posits that genetic differences in infertile parents might predispose their children to a higher risk of birth defects, with some studies indicating that infertile men often exhibit missing genetic material on the Y chromosome, which may correlate with certain defects.

Additionally, the study identified that the prevalence of twins and multiple births among women undergoing fertility treatments contributes to this increased risk. It was found that twins and multiples, regardless of conception method, had the highest incidence of heart defects. Multiple births are more frequent with treatments like IVF since doctors may transfer several embryos to enhance the likelihood of a successful pregnancy. However, advancements in implantation success rates and growing awareness of the risks associated with twin pregnancies have led to a decline in this practice. As of 2020, over 80 percent of procedures involved single embryo transfers, a significant increase from around 20 percent in 2011, according to the Centers for Disease Control and Prevention.

Dr. Wennerholm expressed hope that forthcoming data will indicate a reduction in heart defects as a result of this shift. “I think that’s an important message to clinicians and to patients: You should go for a singular embryo transfer,” she concluded.