Most likely it's from an organization specifically dealing with pregnant transgender people. Or possibly some guidance on medical documentation somewhere, which is where "birthing person" came from.

From February of this year.

alright I'll be the first to say it: this is a dumb language change

Is it? Sounds like an attempt to stop bigots from denying services based on gender.

In the specific case/context of IVF taken in isolation it may not even be that dumb, but taken as part of the overall "inclusive language" trend (birthing person, uterus haver, menstruator, chest feeding, etc.) it just adds fuel to the fire. Many women have been warning about this for several years

As a transgender person who could become pregnant and knows many who have, this is not a term that we use. “Pregnant person” sure. Everyone calls people pregnant. This is a normal term regardless of gender. Nobody calls anyone “inseminated”

Please do not attribute what really does sound like someone’s fetish to us as a group

I didn't. I suggested transphobes dug it up from some specific place like an org trying to be sensitive to people under stress. Someone else linked articles indicating it was Wisconsin Democrats implementing gender neutral legal protections for IVF procedures.

I bet their AO3 history is wild.