Strictly speaking, it is not possible for a biological man to get pregnant, because men do not have female reproductive organs. However, biological women who undergo gender transition are still able to become pregnant if they still have healthy female reproductive organs.
Despite the advancement in gender transitional medical procedures, it will always be impossible for a biological man to become a biological female, and be impregnated.
A biological woman who becomes a trans-man will never be able to impregnate a woman. A trans man does not produce the sperm that is required.
A biological man, who transitions to a trans-woman, will never be able to become pregnant. Such a person does not have the female reproductive organs to do so.