My baby was born with severe neumonia. My wife gbs was negative but still received antibiotics during labor cause she was + in the past. What happened?

GBS. Having negative gbs status does not completely rule out pneumonia from gbs. Mom can acquire gbs later in pregnancy. Besides gbs, there are many other reasons for baby having pneumonia. Other common pneumonia is related to e coli.
Can't say for sure. Pneumonia is a problem in the lungs. It can be caused by different kinds of bacteria (including gbs). It can be caused by "aspiration, " which is when the baby inhales something it shouldn't into the lungs (like meconium, which is baby poop), or from other causes. The fact that your wife got antibiotics might be unrelated to what happened to your baby. Depends on the type of pneumonia.