The BBC has the responsibility to make sure that the news uses standard English so that it can be understood. And that it is not confusing.
This was also a message giving health warnings. If a message is to be received by those who need it most, then the correct term is indeed pregnant women. If a person who has a philosophical belief that doesn't reflect material reality cannot understand the common usage of the words of their primary language because they put mental blocks on messaging, even vital warnings, unless it complies with their personal philosophical belief, they need to seek better mental health support.
People with transgender identities are people who share a philosophical belief about themselves and it is one that doesn't reflect material reality. This is because there is no biological or neurological marker that has been found.
No other group has their philosophical belief (one that doesn't have a basis in material reality) centred in language used by the BBC where the BBC changes the language that refers to all people to suit that one group.
But thank you for pointing this out. Because the more you and other posters point this type of thing out, the more that the general public understand.