There's a distinction drawn (typically) between transsexual people, who have had a major intervention to physically alter their body morphology, and transgender people, who haven't necessarily: they may just say they are and identify with the gender that does not match their developmental sex.

Furthermore, people are labeled by what they are changing to, not from.

Therefore, a "transgender man", or "trans man" for short (and with additional ambiguity) may actually be morphologically completely female and be hormonally female, to the point where they can give birth.