Babies conceived through certain fertility treatments, including in vitro fertilisation, are more likely to have major heart defects, although cases are still rare, researchers reported recently in the largest study of its kind.
The research, which included medical records of more than 7m Nordic children, also bolstered evidence that IVF is associated with a small but significant uptick in birth abnormalities.
“It’s an increased risk, but the absolute risk is very small,” said Dr Ulla-Britt Wennerholm, the senior author of the paper and a professor of obstetrics and gynaecology at the University of Gothenburg in Sweden.
“I think that’s a reassuring finding, actually.”
The New York Times reports that the study, published in the European Heart Journal, focused on children born between 1984 and 2015 in Denmark, Sweden, Norway and Finland as a result of a class of fertility treatments called assisted reproductive technology (ART), the most common of which is IVF.
The risk of a major heart defect was about 36% higher in this group than in children who were naturally conceived. But the defects were still uncommon: less than 2% of infants conceived through ART were born with major heart defects.
The risk of heart defects didn’t change based on whether the parents underwent ICSI, a procedure in which sperm is injected into an egg, or IVF, which allows the sperm to penetrate the egg naturally in a lab dish.
It also did not make a difference whether the implanted embryos had been frozen for later use or the doctors implanted the embryos shortly after the eggs were fertilised in the lab.
The link between IVF and birth defects of all kinds, including those that affect the muscles, genitals and gastrointestinal tract, has been well established in the scientific literature, said Dr Jeffrey Kuller, a maternal-foetal medicine specialist at Duke Health.
The reason for that association isn’t clear, though.
One theory is that something about the IVF process – which involves extracting a woman’s eggs, fertilising them in a lab and then transferring the resulting embryo into the woman’s uterus – may be responsible.
Another theory, Kuller said, is that infertile parents have genetic differences that make their children more likely to have birth defects. For example, there is evidence that infertile men are more likely to have missing genetic material on the Y chromosome, which may be associated with some defects.
The high prevalence of twins and multiple births among women who undergo these fertility treatments may also contribute to the higher risk. Twins and multiples, however they were conceived, had the highest risk of heart defects, the study found.
Multiple births are more common with fertility treatments like IVF because doctors sometimes transfer more than one embryo to increase the odds of a successful pregnancy. Even single-embryo transfers are more likely to divide into twins than in a naturally conceived pregnancy.
But as the dangers of twin pregnancies have become clearer and implantation has become more successful, the practice has become less common.
In more than 80% of procedures in 2020, just one embryo was transplanted, up from about 20% in 2011, according to the US Centres for Disease Control and Prevention.
Wennerholm said she hoped that more recent data would show a drop in heart defects as a result of that shift. “I think that’s an important message to clinicians and to patients: You should go for a singular embryo transfer,” she said.
Study details
Congenital heart defects in children born after assisted reproductive technology: a CoNARTaS study
Nona Sargisian, Max Petzold, Eva Furenäs et al.
Published in the European Heart Journal on 26 September 2024
Abstract
Background and Aims
Children born after assisted reproductive technology (ART) have worse perinatal outcomes compared with spontaneously conceived children. This study investigates whether children conceived after ART have a higher risk of congenital heart defects (CHDs) compared with children born after spontaneous conception (SC).
Methods
All 7 747 637 liveborn children in Denmark (1994–2014), Finland (1990–2014), Norway (1984–2015), and Sweden (1987–2015), where 171 735 children were conceived after ART, were included. National ART and medical birth registry data were cross-linked with data from other health and population registries. Outcomes were major CHDs, severe CHDs, 6 hierarchical CHD lesion groups, and 10 selected major CHDs, diagnosed prenatally or up to 1 year of age (Denmark, Finland, and Sweden) and prenatally or at birth (Norway). The association between ART and CHDs was assessed with multivariable logistic regression analysis, with adjustment for available confounders.
Results
Major CHDs were detected in 3159 children born after ART (1.84%) and in 86 824 children born after SC [1.15%; adjusted odds ratio (AOR) 1.36; 95% confidence interval (CI) 1.31–1.41]. Risk was highest in multiples, regardless of conception method. Severe CHDs were detected in 594 children born after ART (0.35%) and in 19 375 children born after SC (0.26%; AOR 1.30; 95% CI 1.20–1.42). Risk was similar between ICSI and IVF and between frozen and fresh embryo transfer.
Conclusions
Assisted reproductive technology–conceived children have a higher prevalence of major CHDs, being rare, but severe conditions. The absolute risks are, however, modest and partly associated with multiple pregnancies, more prevalent in ART.
See more from MedicalBrief archives:
No milestone gaps between IVF-conceived children and their peers, large study finds
Greater CVD risk for children conceived through IVF
Increased risk of certain cancers for children conceived from frozen embryos