I am going through a divorce and my wife is pregnant but she does not know if the unborn child is mine. Will the child be considered mine in a court of law without knowing?

Once the baby is born you get a paternity test.
If you get it done after the baby is born and before the baby is released from the hospital and it is yours then you sign the birth certificate.
IF you can't do that then you can go to family court and they will have a paternity test done and then you can add your name to the birth certificate if it comes back as yours.

Depends on the state, some states may require you wait till the baby is born for a final discharge of the divorce

Some states (MA for example) will presume you to be the legal father even if your divorce is finalized. When my daughter was born my fiancée was asked if she had been married to anyone but me within 300 days of the birth. So if you are married when the child was conceived, you may still be the legal father at birth.

Yeah no matter what I would demand a paternity test right off the bat asap