Children born with a major birth defect following IVF had almost seven times the risk of developing cancer before age six than those born without a birth defect. Children born with a birth defect who were conceived naturally were three times more likely to develop cancer.
Professor Barbara Luke, first author of the study told MedPage Today, 'IVF-conceived children are at about one-third greater risk of birth defects compared to their naturally-conceived counterparts, as well as at higher risk of childhood cancer, although in absolute terms these numbers are small'.
Although the reason behind the increased risk is not fully known, findings from previous studies had shown an increased risk of childhood cancer from some IVF treatments.
'An unresolved question in assisted reproduction research remains the contribution of parental versus treatment factors to adverse outcomes', Professor Luke said.
The study, published in JAMA Network Open, compiled data from children with births registered in four US states, Massachusetts, North Carolina, New York and Texas, between 2004 and 2016, and linked them to birth defect registries, cancer registries and national assisted reproduction databases. Of the dataset, 53,000 children were conceived via IVF; over one million children included in the study were born without fertility treatment.
Children were classified as being born as either a result of IVF or natural conception and were grouped according to the number of defects they had at birth. Around 1.8 percent of the children who were naturally conceived were born with a defect, compared with around 2.4 percent in the IVF group.
For both the fertile and IVF groups, the likelihood of developing cancer before age six was higher in those children born with birth defects, but the risk was amplified in those born following IVF. In both cases, a chromosomal defect conferred a higher risk of cancer than a non-chromosomal defect.
The study team suggest that epigenetic modifications – changes to the chemical structure of DNA that does not change the sequence of the genes themselves – might occur when an embryo is grown in the lab, contributing to birth defects and cancer risk in children conceived via IVF.
Epigenetic modifications also accumulate with age. The parental age for children included in the study was higher for those conceived via IVF compared to those conceived naturally. Parents who conceived with no medical intervention were between ages 18-24, whereas those who had reproductive assistance were mostly 35 and older.
'I think these studies need to move to look for molecular clues' said Professor Logan Spector, professor of paediatrics at the University of Minnesota in Minneapolis, who was not involved in the study.