If a girl is pregnant and her stomach is punched, does the baby die? i've seen this everywhere lately and i'm curious to know.

Not likely: Though theoretically possible due to damage to a small fetus from a severe blow, the nature is more resilient than letting the offspring be wasted with such accidents. In later stage if pregnancy it would be less likely.

Gestational age: there are a lot of factors involved and whether or not abdominal trauma in a pregnant woman will lead to harm to the baby. Any person who is a victim of trauma needs to be seen by a doctor and any contractions or vaginal bleeding reported, however these cases do not always result in mortality because the abdomen and amniotic fluid can provide cushioning.

Depends: It would depend on how far along the pregnancy is? How hard is the punch? Any other issues, e.g., placenta previa? Bleeding tendency in the woman, high blood pressure etc. In short, trauma to stomach can cause fetal death.