There's already been several transmen who have given birth. The most famous is Thomas Beatie. https://en.wikipedia.org/wiki/Thomas_Beatie
Transmen who haven't had bottom surgery are the closest to BL omegas. They identify as and are legally they are recognized as men. Plus the testosterone grows their clits into mini penises and they develop other male characteristics. So while he was assigned female at birth, he was legally and physically recognised as being a man when he gave birth.
Also scientifically not everyone's chromosomes match their bodies. You can be born with a penis or vagina but genetically Of a chromosome level, be of a different gender. Gender is more complicated then just our physical bits.
No probs! :) I just recently learnt about the chromosome thing and thought it was really interesting!
Something else I just remembered is although it's rate but there are people who are born intersexed! So like trans men or women who haven't had bottom surgery, they'll also have a mixture of male and female sexual organs. The most famous intersex person in modern times is the athlete Caster Semenya. https://en.wikipedia.org/wiki/Intersex
If you read the beginning part of Deliverance of the Counter Attack, you know the part where or main man's gets pregnanto? Yea well I've been thinking, our other daddy probably did the do from our main daddie's bottom opening resulting in the beautiful creation of WoWo. So can men with wombs actually give birth from their bum??