Minnesota study finds IVF-cancer link, but researcher says it's small

Children born through in vitro fertilization (IVF) have slightly higher risks of cancer than other children, but a University of Minnesota researcher who found the connection says it shouldn't trouble parents who are considering the infertility procedure or have already used it to give birth.

The largest study of its kind found a 17 percent increased risk of childhood cancers in children conceived through IVF, according to findings published Monday in the journal JAMA Pediatrics.

But almost all of the heightened risk was explained by the number of blastomas — embryonic cancers, which occur in fetuses or young children — rather than other common childhood cancers such as leukemia or lymphoma.

The risk increase was small even for blastomas, said Logan Spector, the U researcher who led the study. The study also couldn't rule out the possibility that the increased cancer risk was due to the underlying causes of the parents' infertility, rather than the use of IVF to overcome them.

"There was no indication that any specific IVF procedure or treatment was associated with these cancers, so there is not really anything patients or their providers should be doing differently," Spector said. "Overall these results should be reassuring to parents who have used IVF."

With IVF, eggs are fertilized in a laboratory and then some of the resulting embryos are implanted in the mother's uterus. The approach has been used with increasing frequency in the United States and in the handful of Minnesota clinics that offer it.

Five Minnesota clinics performed 3,522 cycles of IVF in 2016, and produced 1,221 deliveries and 1,462 infants (reflecting the increased likelihood of multiple births through IVF), according to the U.S. Centers for Disease Control and Prevention.

Spector said he wasn't surprised by the results of his team's study. Doctors have theorized that IVF can sometimes disrupt the process of genetic expression in embryos — which in turn can produce cancer-causing defects. One such genetic disruption is a common cause of hepatic cancers of the liver — and the study found they were twice as likely in children conceived through IVF.

The results agree with two similar but smaller studies conducted in Scandinavia and the United Kingdom that found that IVF presented no heightened risk of most childhood cancers.

The rarity of IVF procedures, and then of children born through the procedure who develop cancer, required the need for a large group to examine the link. The study reviewed 276,000 children conceived through IVF — 321 of whom developed childhood cancers — and compared them within five years of their births with 2.2 million children conceived naturally from 2004 through 2013.

Even with such a large group, the study could only find a weak statistical link between IVF and cancer — although the link specifically with hepatic cancers was stronger, Spector said.

The study also didn't identify any variation in cancer risk by type of IVF procedure, including whether mothers used their own eggs vs. donor eggs, used fresh egg vs. frozen eggs, or waited six days vs. two days to implant the eggs after fertilization.

Jeremy Olson • 612-673-7744