With IVF, the doctor harvests as many eggs from the woman as possible. Then after taking the make sample and cleaning, selecting the semen with best modality , fertilize each embryo. Then let the embryo grow for a couple of days then freeze the embryo until it’s ready to be implanted (likely during the woman’s next cycle). If you choose, and generally for a fee, you can have each embryo tested for chromosome mutations.
After the process your doctor will call you and let you know how many eggs were harvested and how many were fertilized. They can then give you a report card for the embryos that represent likelihood of live birth, chromosome evaluation, male/female etc.
You then make a selection of which embryo (s) to insert.
Obviously, given the expense of IVF it’s hard to imagine a scenario of not telling the doctor to pick the highest rated (male or female) embryo just for best chance of success.
Felt very reminiscent of gattaca. And that was just selecting the best that we produced. I can easily see myself saying yes to “The best embryo you have had a chromosome defect that will likely result in condition X, but we can fix the defect with a small gene modification, and give the child the best chance for a healthy life, should we modify the embryo?”
And then the slippery slope, “we can also improve the odds of higher intellect, being taller , thinner, etc”.