Doctors working for the United Kingdom's government-run National Health Service are being told to stop calling pregnant women "expectant mothers" because it is not "inclusive" to biological women who identify as men.

The trade union representing NHS doctors claims a "large majority of people that have been pregnant or have given birth identify as women," but said a change to remove the word "mother" is necessary because biological women who think they are men can get pregnant.

The Daily Mail revealed an official 14-page manual given to doctors and medical students entitled "A Guide To Effective Communication: Inclusive Language In The Workplace."

"A large majority of people that have been pregnant or have given birth identify as women," the guidebook says. "However, there are some intersex men and trans men who may get pregnant."

"We can include intersex men and trans men who may get pregnant by saying ‘pregnant people' instead of ‘expectant mothers,'" the guidebook adds.

No biological men have ever given birth. The Daily Mail reported the change in policy came after an announcement that a trans man is four months pregnant. Hayden Cross, a biological woman who became pregnant "thanks to a sperm donor found on Facebook," is waiting to have sex-change surgery until after the baby is born.

The British Medical Association, the trade union representing 160,000 NHS doctors, released the guidebook, saying the change in policy was meant to "celebrate diversity."

"I would encourage you all to read and share this guide, and think about how you can apply it in your day-to-day work," said Dr. Anthea Mowat, a senior executive with the British Medical Association. "This is a time where we need to come together to support and protect our colleagues and our patients."

Doctors should also avoid describing babies as being "born man" or "born woman" because those terms "over-simplify a complex subject."

"Neither should they say ‘biologically male' or ‘biologically female,' for the same reasons," the Daily Mail reported. "Instead, they should say the individual was ‘assigned' or ‘designated' male or female at birth."