When can babies hear in the womb?
A baby first responds to sound at about 19 weeks of pregnancy, starting with low tones. By 27 weeks, 96% of babies respond to low sounds, and higher notes follow by 33 to 35 weeks. Your voice reaches your baby more strongly than anyone else's, because it also travels through your body. Talking, reading and singing are all your baby needs.
On this page
When hearing switches on
The best map comes from a careful study in Belfast, Northern Ireland. Researchers Hepper and Shahidullah played pure tones near pregnant women's bellies and watched for the baby's movements on ultrasound. Here's what they found:
| Weeks of pregnancy | What babies responded to |
|---|---|
| 19 weeks | The first response, to a low 500 Hz tone |
| 27 weeks | 96% of babies responded to low tones (250 and 500 Hz) |
| 33 weeks | Every baby responded to a middle tone (1000 Hz) |
| 35 weeks | Every baby responded to a higher tone (3000 Hz) |
As the weeks went by, babies also needed quieter and quieter sounds to react. The threshold dropped by 20 to 30 decibels. So hearing doesn't flip on like a light. It fades in, low notes first, like a dimmer being slowly turned up.
The CDC's workplace-safety institute (NIOSH) gives rounder numbers: the ears form by about week 20, and babies start responding to sound around week 24. Both pictures agree on the main point. By the end of the second trimester, your baby is listening.
One honest note. A movement in response to a tone shows the baby detected a sound, not that it understands anything. What starts now is simpler: the brain begins filing away the sounds it hears most.
What the womb sounds like from inside
Put your head under the bathwater and ask someone to talk to you. That's close. Your body works like a thick, wet filter. Researchers who placed tiny microphones inside the womb found that body tissue acts as a "low-pass filter": very low tones pass through with little loss, while higher tones lose much more of their loudness.
What survives is the melody and rhythm of speech: the rise and fall of a voice, the beat of sentences, the pauses. Many crisp, high consonant sounds get blurred. Still, speech inside the womb is clearer than you'd think. When adults listened to sound recorded inside a pregnant woman's uterus, they could pick out about 30% of French speech sounds, and the melody came through even better.
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Why your voice comes through best
Your voice reaches the baby two ways. It travels through the air and the belly wall like everyone else's. It also travels through your own body, from your throat and chest, through bone and tissue. Recordings from inside the womb pick up the mother's voice more strongly than other voices. You are the main channel.
And babies are learning from it. Before birth, babies' heart rates rose to a recording of their own mother reading and fell to a stranger reading the same passage. After birth, newborns prefer their mother's voice; see do newborns recognize their mother's voice. In Finland, babies who heard a made-up word ("tatata") about 25,000 times from week 29 showed a stronger brain response to it after birth. That shows the brain stores sounds it hears often. It doesn't show better language or IQ later, and you don't need recordings. Your ordinary voice does the job.
Babies even pick up the sound of your language. In a study in Tacoma, Washington, and Stockholm, Sweden, newborns about 30 hours old reacted differently to vowels from a foreign language than to vowels from their own (40 babies in all). And in Germany and France, researchers found that newborns 3 to 5 days old cried with the melody of their parents' language: rising for French babies, falling for German ones. If your family speaks two languages, use both. Your baby is tuning in to the sounds you actually use.
What to do with this
You don't need equipment, a script or a special voice. Talk to your baby the way you'd talk to someone you love who's in the next room.
- From 14 to 18 weeks: start a daily talk time so it's a habit before hearing comes online.
- From about 19 weeks: narrate your day, read aloud a few minutes, and sing. Singing is pure melody, which is what passes through best. Pitch doesn't matter.
- From the late second trimester: pick one short, rhythmic story to repeat twice a day. Our page on reading to your baby in the womb explains why.
- Bring your partner in: a few minutes a night, close to the belly, normal voice. A partner's voice does get through, just less directly than yours.
Ten minutes a day is plenty. See talking to your baby in the womb for ideas and example phrases.
What to avoid
The same open channel that lets your voice in also lets loud noise in. NIOSH advises pregnant women to stay out of areas louder than 115 dBA, roughly chainsaw level, even with hearing protection, because your earplugs don't cover the baby's ears. Low, rumbling noise and vibration travel through the body most easily, so don't lean your belly against noisy or vibrating machines.
Skip belly headphones and bump speakers. There's no evidence they help, and they put a sound source right against your belly, which is what NIOSH says to avoid. Ordinary life (traffic, a barking dog, a loud toddler) is fine. For concerts and noisy jobs, see loud noise during pregnancy.
Do this
- Pick a set 10 minutes a day (breakfast, the commute or bedtime) to talk, read or sing to your bump.
- Speak your home language or languages naturally; no recordings needed.
- Ask your partner to talk to the bump for 5 minutes a night, close and in a normal voice.
- Move any speakers or headphones off your belly and keep music at normal room levels.
- Stay well back from speakers at loud events, and leave if you feel the bass in your chest.
When to ask your doctor
Check with your doctor or midwife first if…
- Your job puts you around loud machines, amplified sound or strong vibration all day (ask your employer and doctor about a quieter task).
- You're thinking of using any device that plays sound against your belly.
Call your doctor now if…
- You haven't felt any movement by 24 weeks (tell your doctor or midwife).
- Your baby is moving less than usual, the pattern changes, or you can't feel movement (call your doctor, midwife or labor unit now, day or night, or 911).
This page is general information, not medical advice. Every pregnancy and every child is different. Ask your doctor, midwife or pediatrician before changing supplements, diet or care.
Grow a Genius
In the book: Chapter 10: Second Trimester: The Baby Starts Listening
Chapter 10 maps weeks 14 to 27 week by week, with a daily bump-talk routine, the partner's role, the touch game for first kicks and the noise rules, and The Genius Journal gives you a place to track it.
- The 7 Genius Builders, stage by stage
- 16 printable guides, including the Prenatal Label Decoder
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People also ask
Can my baby hear me talking at 20 weeks?
Possibly the low parts of your voice. Babies first respond to low tones at about 19 weeks, and NIOSH says the ears form by about week 20. Hearing keeps improving, and by 27 weeks almost all babies respond to low sounds. Talking now builds the habit.
Can babies hear music in the womb?
Yes, especially the melody and beat, which pass through the body better than high notes. In a Finnish study, babies who heard a melody often in late pregnancy still showed a stronger brain response to it at 4 months. Keep music at normal room levels, not on your belly.
Can my baby hear my partner's voice?
Yes. In a Canadian study, babies' heart rates rose to their father's voice before birth, just as they did to their mother's. A partner's voice has to come through the air and belly wall, so it arrives less directly than yours. Close and normal volume works best.
Do belly headphones help my baby learn?
There's no evidence they do. NIOSH advises against placing sound sources against your belly, and the Finnish researchers who studied womb learning warned that loud sound may harm the developing hearing system. Your own voice is the best prenatal audio there is.