Thursday October 31 2013
Babies begin to hear around the 27th week of pregnancy
"Babies remember melodies heard in womb, study suggests," reports The Guardian. The study found that babies exposed to the lullaby "Twinkle, twinkle little star" while in the womb showed signs of remembering it up to four months after birth.
The study involved two groups of mothers:
- the learning group – mothers who played the well-known lullaby "Twinkle, twinkle little star" in late pregnancy
- the control group – mothers who did not play music regularly
After birth, researchers found signs that babies in the learning group showed signs of "remembering" the lullaby.
The brain activity of babies whose mothers regularly played the lullaby in pregnancy was stronger when similar music was played after birth and at four months.
The researchers suggest prenatal exposure to music may influence brain development at a critical period for the development of the auditory system.
The researchers also speculate that being exposed to less soothing sounds during pregnancy may have a negative effect on a child's development, but this hypothesis is unproven.
The results of this small study are of interest, but it does not prove that prenatal exposure to music improves a baby's brain development, memory or hearing. Pregnant women should not feel obliged to play lullabies to their unborn babies every day.
Where did the story come from?
The study was carried out by researchers from the University of Helsinki and the University of Jyväskylä, Finland and the Finnish Institute of Occupational Health.
It was published in the peer-reviewed journal PLoS One. PLoS One is an open access journal, so the article is free to read online or download.
It was funded by the Academy of Finland, the ERANET-NEURON project Probing the Auditory Novelty System (PANS), the University of Helsinki and the Finnish Cultural Foundation.
As the study is about babies and pregnancy, it attracted a fair amount of media coverage. The Daily Telegraph's assertion that babies can "learn" their first lullabies in the womb is an exaggeration of the study's findings, as is its suggestion that playing music while pregnant could help develop an unborn child's hearing.
The Mail Online's claim that the brains of those who hear music before birth "lit up" more on hearing the lullaby later also slightly exaggerates the findings. It is unclear whether exposing a child to music in the womb has any lasting benefit.
What kind of research was this?
This was a controlled experiment that looked at whether prenatal exposure to a melody during the third trimester of pregnancy could affect measurements of babies' brain activity when the music was replayed at birth and four months.
The researchers say that a newborn has surprisingly extensive experiences of the surrounding world. In particular, they seem to react to sounds during the foetal period and respond distinctly to them after birth. The researchers also say that foetal auditory learning becomes possible in humans by 27 weeks of pregnancy.
Previous research has focused on the immediate outcomes of foetal auditory learning after birth. They point out that their study looks at the possible "learning effects" by following infants four months after birth.
What did the research involve?
The study recruited 12 women with healthy singleton pregnancies (the learning group) for its experiment and included 10 of them in the analysis. A further 12 mothers, all with healthy newborn infants, were recruited as a control group.
In this group, the mothers did not regularly play music during pregnancy. The researchers used data from 11 of these infants for the initial experiment and eight for the follow-up. Participants were not included because of technical issues or excessive movement of the babies.
At birth, the hearing and health of the infants in both groups was tested and all were found to be normal. Their gestational age, birth weight, health and the age at the time of the experiment were all recorded.
Pregnant women in the learning group played a learning CD at home at a loud volume five times each week from 29 weeks of pregnancy until birth. The CD contained three short excerpts of several musical melodies alternating with speech phrases. One of the tunes was a 54-second long melody of "Twinkle, twinkle little star" played on a keyboard. Other different musical sounds were also included, such as a classical piece by the Finnish composer Jean Sibelius.
The mothers in the learning group played the CD between 46 and 64 times (average 57) overall. The "Twinkle, twinkle little star" melody was repeated three times on the CD, so the foetuses would have been exposed to it between 138 and 192 times (mean 171).
After birth, and again at four months, a modified version of the "Twinkle, twinkle little star" melody, in which some of the notes were altered, was played to the infants in both groups nine times through loudspeakers. Speech phrases and other musical sounds similar to those on the learning tape were presented between the melodies.
The researchers then placed electroencephalogram (EEG) electrodes on the babies' scalps. An EEG is a device used to measure brain activity. They used the EEG to measure what is known as event-related potentials (ERPs) while the music was playing. These are essentially a sign of the brain responding to a previously learned signal, in the same way that you would respond to hearing your name shouted in a crowded railway station.
The researchers also measured a further component of ERPs called mismatch negativity (MMN), which they say can detect brain reactions to the new notes being played in the altered melody – or, in lay terms, recognising when somebody plays a bum note that sounds out of tune.
The data from the experiment was analysed, taking account of when the babies were asleep.
What were the basic results?
Researchers found that both at birth and at the age of four months, babies in the learning group had stronger ERPs to the unchanged notes in the melody than the control group.
The more often the newborns in the learning group had heard the CD, the larger the ERP amplitudes to both the changed and unchanged notes at birth, although this effect was no longer seen at four months.
No differences between the two groups were found for reactions to the MMN.
How did the researchers interpret the results?
The researchers say the results show that extensive prenatal exposure to a melody induces "neural representations" that last for several months.
In an accompanying press release, they point out that the period from 27 weeks of pregnancy to six months of age is critical to the development of the auditory system, and that prenatal exposure to musical melodies may influence brain development during this period.
Perhaps more importantly, they also suggest that adverse sound environments during pregnancy – such as a noisy workplace – may have long-lasting detrimental effects.
Also, it is possible that foetal exposure to more soothing, structured sounds might be beneficial to at-risk infants who show signs of impaired auditory processing.
This very small study suggests that babies whose mothers played a lullaby during the later stage of pregnancy seemed to have more brain activity in reaction to that music when it was played at birth and four months.
This suggests that foetuses may remember sounds heard in the womb, but it does not prove that exposure to music in the womb enhances the auditory system or later brain development.
Also, the researchers only used one measure of brain activity called ERP. Whether this is an adequate reflection of neural response to music is uncertain. For example, they did not look at possible behavioural responses to the music, such as thumb sucking or head turning.
It is also possible that the babies differed in ways that might have affected the results of the study, such as general health or brain development.
Perhaps the most important thing to consider if you are pregnant is your own wellbeing. Playing music that you enjoy and that relaxes you may be a better option than listening to a lullaby on a loop.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.