As long as frequently is considerably less than 1% of all births in the US (and significantly less in other parts of the world). 1.5-2% of children are adopted

As long as frequently is considerably less than 1% of all births in the US (and significantly less in other parts of the world). 1.5-2% of children are adopted in the US. About 50% of those children's parents adopted due to infertility, of which an even smaller fraction is voluntary infertility. I wouldn't say that is something that humans due frequently, and is probably limited to a small set of cultures, and an even smaller subset of parents with both the knowledge and fortitude to make that decision. I'm an adoptive parent and know several dozen other adoptive families. I have never personally met someone who chose to adopt to avoid the risk of passing on genetic abnormalities.