Jean Smith

Freezing eggs at a younger age becomes even more important with polygenic embryo screening.

We've had genetic screening for conditions like Down syndrome and sickle cell anemia for decades, but starting in 2019, it became possible to screen your child for risks of all kinds of things.

Parents who go through IVF can now boost their children's IQ, decrease their risk of diseases like Alzheimer's, depression and diabetes, and even make their children less likely to drop out of high school by picking an embryo with a genetic predisposition towards any of these outcomes.

But the size of the benefit of this screening depends significantly on the number of embryos available to choose from, which declines almost linearly with age.

The expected benefit of embryo screening declines as a result.

There's an image here.

the father's age actually affects the expected benefit as well.

But the decline is slower and most of the biological downsides of an older father show up as increased risk of developmental disorders like serious autism.

It is possible to compensate for this to some degree by doing more IVF cycles, but by the late 30s when the modal woman is freezing eggs, even this strategy starts to lose efficacy.

This is just one more reason why the standard advice to wait until your mid-30s to freeze eggs is wrong.

Heading What about technology to make eggs from stem cells?

Won't that make egg freezing obsolete?

More clued in people might point out that there are several companies working on making eggs from stem cells, and that perhaps by the time women who are 20 today reach the age at which they're ready to begin having kids, those eggs will be useless because it will be easy to mass manufacture eggs by that time.

There are three reasons why the possibility of stem cell-derived eggs should not give much comfort to women who want to preserve their fertility or have genetically enhanced children.

Subheading.

We don't know with certainty how long it will take to develop this technology.

It's not trivial to develop eggs from stem cells.

One of the people running a company commercializing this tech believes the tech will be ready for human use in about six to eight years, but as always, there is significant uncertainty about exactly how hard each one of the required steps will be.

Subheading Stem cell-derived eggs are probably going to be quite expensive at the start.

New technologies, especially those that go inside human bodies are pretty much always expensive and that will almost certainly be the case for stem cell derived eggs.