..allow the child to be adopted.
What other choice is there.?
well...they cannot medically carry them to term.
They do not want them adopted out.
You are talking about couples willing to spend thousands of dollars to “have” children, and then asking them to “give up” children - I know intellectually it is easy to point out the obvious, but emotionally they don’t want to “give away” their own kids.
The embryos sit there where they are.