If the intention of this were to remind doctors that a pregnant woman is still a person in her own right, not just a vessel for her unborn child, I could see the point. But in that case, 'pregnant woman' would achieve exactly the same thing, without appearing to wipe out the woman in the equation.
I remember my mum getting very cross if a doctor called her 'Mum', during any appointment to do with pregnancy, labour and delivery, the postnatal period or when taking either dsis or I for an appointment. She felt - and I agree - that there was far more to her than just a mother, and that by failing to acknowledge that, by using her name, the doctor was depersonalising her and reducing her to just a mother.
It wasn't that she didn't know she was a mother - but she wanted to maintain her own individuality as well.
So a policy that made doctors think 'this is a woman who is pregnant, but she is not just the vessel for the baby, she is still a person in her own right', might be no bad thing - but if it is in response to trans activists demands, then I agree that it is a very bad thing indeed.
I have said on another thread (the 'chestfeeding' one) that I fear that a certain section of the trans activist community is trying to advance their own cause by wiping out the identity of cis women (a term I hate, but use here because it describes the group of people they want to vanish).
That thread is about wanting to relabel breasts as chests, this one is about relabelling pregnant women/expectant mothers as pregnant persons - but the effect feels the same to me. This is what I said on the other thread:
"This feels as if some trans activists want women - cis women - to disappear. We don't fit in their narrative, so we are not wanted. We should be made to give up anything and everything to the trans active community, and simply not be, any more.
Taking away our terms for our body parts feels like wanting to erase us completely."