When can a fetus hear? Everyone knows babies start to hear between 23 and 27 weeks of pregnancy. At least your partner knows, because she already read it in What To Expect. Ask her, it’s fascinating stuff. What’s been lesser known until recently is that they remember things they hear during that final trimester. Now when you claim your kid liked the Beatles before they were even born, you’ll have research to back it up.
The idea was studied in a 1988 report that suggested newborns recognized the theme song of their mother’s favorite soap opera. While that’s so funny you might not care if it’s true, scientists weren’t satisfied with those behavior-based findings, since babies are basically tiny drunk people whose behaviors are totally unreliable and notoriously hard to replicate in a lab setting.

Instead, cognitive neuroscientist Eino Partanen and his partners at the University of Helsinki used neural evidence in their study. They had pregnant women play a recording of a made-up word, “tatata,” multiple times a week during their last trimester — more than 25,000 total times on average. The repetitions were interspersed with music and the middle syllable was varied, because there’s a fine line between research and using sounds as a form of torture. After birth, the infants were outfitted with EEG sensors that showed their brains recognized the word and its variations, while infants in a control group did not.

The group that heard and recognized the word also showed neural signals for recognizing vowel and pitch changes and syllable differences; those whose mothers played the recording most often showed the strongest signals. Researchers claim this proves that the fetus can learn more detailed information than when General Hospital is on, and more importantly that memory traces are detectable after birth.
Remember, although they’ll recall hearing everything from your voice to In Utero in utero, listening to music won’t make your baby any smarter. Also, no headphones on the belly. Too much noise can overstimulate developing brains, interfere with auditory systems, and disrupt sleep cycles, which are disrupted more than enough naturally. Normal sound carries well through the mother’s abdomen, like the sound of someone talking with their mouth covered. Try it with your partner to get a sense of what your baby experiences. Just know they might start encouraging you to do that every time you speak.