Can transgenders impregnate?

Well first off, calling people "transgenders" is pretty offensive. "Transgender" is an umbrella term for people who feel that their gender does not match their biological sex. There are people who are transgender who do not identify as male or female, but to answer your question:

Transgender women, meaning male to female transgender people (who have been born in a male body, but identify as female, present as female, and feel as though they really are female CAN still impregnate someone ONLY IF they have not yet taken hormones or had sexual reassignment surgery. Many transgender women eventually take hormones to make themselves look more female, and those hormones can lead to infertility. But a pre-hormone transgender woman can impregnate someone, because she still has a penis and can ejaculate sperm.

Transgender men, meaning female to male transgender people (who have been born with a female body, but instead identify as male and present as male and are to be treated as male) CAN still GET pregnant if they have not taken testosterone, or if they have not yet taken enough testosterone to get rid of that function. Most transgender men eventually take testosterone to make them look more masculine, and this can eventually cause infertility. Some men also get sexual reassignment surgery (sex change surgery) but if they DON'T take testosterone or have genital surgery, and they still have vaginas and menstrual cycles, then they can still get pregnant.

You might instead be thinking of intersex individuals when you asked this question. Intersex is someone born with an XXY chromosome and often has both male and female genitals (some combination). This is NOT the same thing as transgender. Whether or not they can impregnate/be impregnated is situationally dependent on individual bodies.