Hi, you suggested freezing embryos instead of eggs. However, a recent study found that frozen embryo babies are 2.5 times more likely to develop cancer. At the same time, a review article on IVF comes to the following conclusion (likely due to epigenetic factors):
IVF is associated with an increased health risk for the offspring in the form of malformations, functional dis- orders, and a poorer peripartum outcome. This is possibly caused by parental factors, but also by factors related to the IVF technology used. [...] Consequently, IVF should only be perfo
Thank you for leaving such a thought-provoking comment. I've spent a couple hours reading through the study you posted tonight as well as others linked to by the authors.
I don't see the claim about a 2.5x increased risk of cancer anywhere though. From the findings section:
So the risk of cancer was 8% higher in those born after ART, and 59% higher for frozen embryos vs fresh embryos.
I think the generally higher disease prevalence among IVF couples probably explains the 8% increase for ART in general, though the 59% increase they see for frozen embryo transfer is surprising.
Looking more into the study it looks like about a quarter of the effect is driven by the higher rates of twin births in IVF, which are much less common nowadays.
This study uses data that is also quite old; they include cycles going all the way back to 1984 or 1994 for some countries. The rate of embryo freezing at that time were quite low, as evidence by the huge difference between hazard ratios for all ART and frozen embryo transfer. If frozen embryos made up a higher proportion of the births you would see a smaller difference between all ART relative to spontaneous conception and frozen embryo transfer relative to spontaneous conception.
Here's another study that found higher risk of neoplasms among embryos that were transferred fresh. Granted, this was a smaller study, so I'd lean towards believing your study.
There's also a graph in the study which seems to show the relative cancer risk for frozen embryos declining over time:
Though this could just reflect fewer twin births. And the confidence interals are such that it's hard to be certain the effect is real.
Another possible confounder here is maternal age. The average age of mothers in ART were older than those in the spontaneous conception group by about 4 years. You can see in this study that maternal age is significantly associated with higher childhood cancer risk. So this could explain another 5-10%, particularly if the
Hi, you suggested freezing embryos instead of eggs. However, a recent study found that frozen embryo babies are 2.5 times more likely to develop cancer. At the same time, a review article on IVF comes to the following conclusion (likely due to epigenetic factors):
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