Maybe not the best idea, depending how far gone she is. I had to tell mt former best friends pregnant girlfriend her bf of 4 years had been cheating on her with numerous one nighters and trying to find a second girlfriend. He had kept her secret (he had moved 4 hours from home to go to uni, she was back in their hometown) but she contacted me after i had called him "hun" (a harmless nick i call all friends) on his fb when i wished him luck with an operation. She was already 4 months gone so too late to abort, and i was scared the stress of the truth may cause her to miscarry, so i didn't tell her he was pretending to be single and hooking up with random girls, or about his failed attempt to make me his girlfriend but i wasn't interested. The guilt ate at me, i finally told her when she was 8 months and the baby stood a good chance of being fine should complications come from the stress but i couldn't let her give birth especially with him there not knowing. I felt so guilty but she was so lovely, despite the fact i was the girl giving her this awful news she was so polite and thankful.