Freddy McConnell made a statutory declaration to a GRC panel to “live as a man” then was pregnant within weeks. No one is saying women who don’t or can’t get pregnant aren’t women, people are saying that declaring your intention to “live as a man” is meaningless if it means doing the most woman thing possible.
And that’s not to say to be defined as “woman” you have to get pregnant, it is to point out the obvious: that “woman” is defined as an adult human female, a female being one of the two sexes, the sex evolved to produce large non-motile gametes and give birth. If you were trying to explain to visiting aliens what is the single most conclusive difference between the two human sexes that can’t be open to interpretation, it would be this. It couldn’t be hair, or face, or even breasts, because there is too much overlap. But the two completely different roles in human reproduction is unequivocal in their description of the differences between males and females. If you produce small, motile gametes - sperm - there can never be a single doubt, not a single overlap. That alien species trying to figure us out would know that person is male, no ifs, no buts. And if you produce non-motile gametes and get pregnant, unequivocally female.
So getting pregnant is the single most discerning biological act that signals a person is female, ie the most woman thing someone can do. If that process isn’t fully functional 
, it still signifies “of the female sex”, in the same way that the observing alien species would not look at a person with one leg and come to the conclusion that humans might not be a bipedal species.
A man cannot get pregnant.