Coming back to the thread topic, I would like to answer this first post by qwerty:
"isn't the general consensus that gender is a social construct and therefore there is no such thing as innate manhood or womanhood? If that is the case then surely it is legitimate to term this man a 'man', a 'transman', a 'woman' or anything else he prefers?"
You are confusing sex with gender.
Man = Adult human male
..... where Male = Of the sex that can make sperm.
Woman = Adult human female
..... where Female = Of the sex that can bear young or make eggs.
Gender = Girls like pink / boys like blue, girls like dresses and glittery stuff, boys like machinery and trains, etc.
In other words, gender is a social construct. Biology is not a social construct. It's the DNA in every cell and your organs, including your genitals.
The pregnant "man" in the OP is still female and will continue to be female even after a hysterectomy, double mastectomy, years of Testosterone injections etc because that "man" will never be "Of the sex that can make sperm" and will always be "Of the sex that can bear young or make eggs".
Sex is biology and it is not possible to change it by wishing yourself something else. Gender is a social construct and it is possible to put on a dress, grow your hair long, paint your nails, act more feminine etc. These two things are completely different and you really need to start differentiating between them if you are going to hang out on FWR.