Gay people can't produce children. Some other person can produce a component to a child and they stick it in the gay person - but the gay couple did not produce that child. It's why it's called ARTIFICIAL insemination.
"Artificial" is the operative word there.
Which reminds me of a Family Guy episode where two gay people were getting artificially inseminated.
"We're going to need some sperm and an applicator shaped like Jodie Foster's knuckles"