Danish study in JAMA links frozen embryo transfer and ICSI to higher childhood cancer rates, though absolute risk stays low

A registry study published in JAMA on 21 October 2026 by researchers at the Danish Cancer Institute re-examined whether children conceived with assisted reproductive technology (ART) have a higher risk of cancer.

What they did

• Study type: an observational cohort study using Danish national registries — an extended follow-up of the group’s 2019 analysis.
• 1,086,136 children born from 1996 to 2012, of whom 37,228 were conceived with ART, followed until age 20 or the end of 2023 (median follow-up about 20 years). There were 3,736 cancers in total.

Main findings

• Overall, cancer incidence was 23.6 per 100,000 person-years after ART versus 18.3 without it — an adjusted 26% relative increase.
• By method, frozen embryo transfer was associated with about 2.2 times the rate and ICSI (injection of a single sperm into the egg) with about 1.5 times; conventional IVF showed no increase.
• In absolute terms, lead researcher Marie Hargreave told Inside Precision Medicine the rate was roughly 41 cases per 100,000 children per year after frozen embryo transfer and 28 after ICSI, versus 18 without ART. She called it “not a reason for alarm” but relevant when treatment options are discussed.
• Similar results among children of women with a history of infertility suggested to the authors that procedure-related factors, rather than infertility itself, deserve further study.

Limitations

An observational study shows associations, not causation. Some estimates for specific cancer types rest on very few cases. The children were born in 1996–2012, and practice has since changed (for example, vitrification and blastocyst transfer), so the authors say the risks may not be the same with current protocols; a larger Nordic dataset is planned. People considering fertility treatment should discuss options with their doctor.