Not usually, b/c they swab the babys mouth or do blood work. You can't draw blood from a fetus, only amniotic fluid

Newborns are readily tested by collecting blood from the umbilical cord on the day of birth. Under special circumstances, dna paternity testing can be performed on unborn children during pregnancy by using amniotic fluids or cvs samples.

How soon usualy? She's only about a month. She is scared she only wants to test the one guy , not her bf. He would leave her if he found out she cheated.