What’s wrong referring to the relevant sex characteristics? Why change language for the exceptional and small population? A man who gives birth is still the mother even if they take a social role of a father later in the child’s development.

Additionally, men don't give birth. Women on cross-sex hormones can give birth. We need to stop with the silliness of "pregnant people".

Because their sex characteristics aren't the relevant thing, the fact that they are pregnant is. The medical field prefers precise terminology. It's only when it comes to trans people that people get weird about it, because they're really using it as an excuse to argue about something else

And maybe that's fine because it isn't a signal of ideology like "pregnant person" is. Don't forget that if scientists were using these terms, they were likely already doing so because of political pressure, so it is good to stop it in cases where it's nothing to do with their research (eg. transgender parturients). Of course it doesn't mean this order isn't ham-fisted, but research is often polluted by politics because it helps get funding as well as researchers are pretty politically biased in some fields.