I would think that if pineapples caused miscarriage there would be a quite a lot of press about them and their ill effects on pregnancy. Since I never heard anything in school, and have yet to read about acidic foods causing miscarriage, I think it is realitively safe to assume those are safe fruits. However, just because I have never heard of it doesn't mean someone out there hasn't conducted some kind of research. My assumption is based on the fact that pineapples and mangoes are widely eaten foods and if they were associated with miscarriage I think the medical field would have caught on by now. Consider this, oranges are highly acidic, and so are lemons and tomatoes. What about the risk with those foods? So, please consider the source when you hear any off the wall advice. The one side effect from acidic foods can be heart burn, but other than that I don't believe acidic foods cause miscarriage. Fruit is a wonderful source of vitamins and minerals so until you see hard evidence of side effects on fetuses -- enjoy your pineapple and mango!!