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Small-Scale Question Sunday for February 18, 2024

Do you have a dumb question that you're kind of embarrassed to ask in the main thread? Is there something you're just not sure about?

This is your opportunity to ask questions. No question too simple or too silly.

Culture war topics are accepted, and proposals for a better intro post are appreciated.

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A couple I know is doing IVF. They have the embryos already but they aren't implanted. I suggested they select the one to implant using genetic testing which a few companies offer at wildly varying costs. Does it really work? Are there downsides? If it can do what's advertised, it would seem to be worth the cost, which is several thousand dollars at most.

If they're already doing IVF I strongly advice it. The cost and risks of the IVF itself are a much higher barrier, so I generally don't advice healthy couples to do IVF just for the genetic testing, but the tests themselves are basically all upside with almost no risk.

For pregnancy prescreening the effectiveness of the tests have been called into question. Embryos are different but might suffer from the same issues?

https://www.nytimes.com/2022/01/01/upshot/pregnancy-birth-genetic-testing.html

Nothing here suggests the tests are ineffective. For a rare condition correctly predicting the fetus has the condition 15 times out of 100 implies the test must very accurate. It's the same thing where if you have a 99% accurate test for a condition that only 0.1% of the population is affected by then given the test says you have the condition you only have a 10% chance of actually having the condition.

Ineffective was not the right word, but it seems that some of the tests give a lot of false positives. If using it to screen embryos you'd delete a lot of healthy ones. If you have a limited number of embryos or a high rate of failure of embryo to pregnancy it might not be wise to use this as screening criteria.

More information is always better. They could decide to still use all the embryos but just try the best ones first.

That's generally not how these tests are used. Usually your number of embryos is higher than the number you'd actually want to implant, so you have to have some criteria. In many cases, this is still done with first some hard cut-off by deformities, down syndrome, etc., and then of the remaining ones it's either plain random or basically by visual inspection. Further genetic testing can help rank the remaining ones instead so that you can implant the one(s) that actually have a better chance at a healthy life. Nobody forces you to discard more embryos than you want, it's usually just extra information that you can still decide to either use or not.

I would like to know the answer to this as well.