According to BabyCenter.com, playing music for babies in the womb has no proven positive or negative effects. Some studies show that fetuses may breathe in rhythm along with music, but other researchers question whether these findings are actually accurate. Playing classical music for older children has been shown to correlate to higher math skills, but these studies have not shown conclusive evidence of this for babies in the womb.
Parents who do wish to play music for their own unborn children should take caution, as exposure to excessively loud sound has been shown to affect babies negatively. The American Academy of Pediatrics reported in the 1990s that numerous studies had found that unborn babies exposed to frequent loud noises were more likely to be born prematurely, born with low weight and born with a greater frequency of hearing loss.
Baby Center recommends playing music on a stereo in the background at no louder than 65 decibels, which is about as loud as background music in a store. Pregnant mothers should refrain from putting headphones on their stomachs as this may overstimulate the baby. Amniotic fluid is a productive conductor of sound, which means that background music penetrates into the womb at a volume that's audible to the fetus. As the results of this practice are still debated, parents should exercise moderation when playing music for babies in the womb.