A small, but significantly increased risk of childhood cancer among children conceived by IVF may concern potential parents.

In vitro fertilization is a stressful process for potential parents, with costs measured in emotional turmoil, medication side effects, and thousands or tens-of-thousands of dollars. Against that backdrop, a new study appearing in JAMA Pediatrics adds to the stress by linking the procedure to a small, but significantly increased risk of childhood cancer.

This is the first US study to really tackle this issue.

Researchers undertook the herculean task of linking the Society of Assisted Reproductive Technology and Clinical Outcomes database (which contains about 90% of all IVF treatments in the US) to state-level birth and cancer registries.

 In the end, that added up to 275,686 kids conceived via IVF. Over around four-and-a-half years of follow-up, 321 of those kids developed cancer. That’s 1 out of 858 kids.

That’s a small number, though not as small as any of us would like. The researchers used similar methods to identify 2.2 million kids born without IVF. In that group, the rate of cancer was one in 1100 kids.

That difference – 1 out of 858 versus 1 out of 1100 just made our standard cutoff for statistical significance. The authors zeroed in on hepatoblastoma and embryonal cell cancers as potentially driving the overall association.

Now of course there are many factors that differed between the kids conceived via IVF and those that weren’t.

Their moms were substantially older, more educated and more likely to be white. The researchers adjusted for these factors but point out that there is no real way to tell whether the increased cancer risk is due to something about IVF or related to the underlying infertility problem in the first place.

But let’s do a thought experiment – what if it is due to IVF.  Does it matter?

Studies like this face an implicit problem of interpretation because using IVF versus not using IVF is not really a choice like choosing drug A over drug B is. Like, for couples who are worried about childhood cancer, what are we saying – just don’t have a kid at all?

Put it this way – using the data in this study I can calculate that to prevent one cancer in a kid under 10, you’d have to stop 3400 successful IVF treatments. I feel like that’s throwing out the baby with the bathwater.

Maybe the results mean we need to be more vigilant about kids who are conceived by IVF? The authors state as much in their conclusion saying:

But… should we?  Probably not. Frankly, I’m not even sure what kind of continued follow-up is being implied here. Routine screening CT scans for hepatoblastoma? The risk of such a strategy in terms of stress, false-positives, and of course costs would seem to me to really outweigh the benefits.

No, studies like this can really only be said to be a first step in finding some pathway that will teach us more about childhood cancers – and that’s what interests me. What can the biology of infertility and IVF teach us about cancer in general, so we can reduce the risk of childhood cancer for everyone?

This commentary first appeared on medscape.com