I(5) – WHAT DO WE THINK CAN BE HEARD INSIDE THE UTERUS? – The foetus receives sounds from the inner body of the mother: heartbeat, breathing and abdominal sounds. The foetus also hears sounds of what the mother is doing (e.g. when she talks or walks in high heels), and also outside noises. But the foetus lives in a soundproofed environment. The organs of the mother and the abdominal wall keeps the foetus isolated.

From the abdomen, part of the sound bounces back outside and the other part is absorbed and distorted by the different layers of soft tissues that form the abdominal wall. The foetus only receives the transmitted part, with less intensity and clarity than in the point of emission.

Studies carried out in sheep, with intrauterine microphones, showed that most of the sound reaches the inside as whispers (approx. 30 decibels). Furthermore, only 50 percent of the words pronounced outside and recorded inside the uterus are intelligible as the words arrive distorted with a different tone.

It’s like the foetus were surrounded by cushions. When we hear people talking in another room, we can still hear it but it’s not clear.

Therefore, we could say that the sound in the uterus is like background noise in the forest. Furthermore, most of the sounds are repetitive, the foetus gets used to it and doesn’t react to them. The foetus can still sleep.

The only way for the foetus to hear as we do, it’s if the sound is transmitted intravaginally.

The vagina is a closed space, therefore there is no sound dispersion. In addition, there are fewer layers of soft tissue separating the foetus from the emitted sound: only the vaginal and uterine wall. We eliminate the barrier of the abdominal wall.

By inserting a speaker in the vagina, the foetus can almost hear with the same intensity as when the sound is emitted. Therefore, thanks to this vaginal device designed and developed for this study, we discovered a way in which the foetus can hear the same way as we do. Now they can hear sound properly, with volume and without distortion.

Can you imagine how many women have told me: “all this time talking and playing music without realising that the foetus cannot hear it”. And all the studies that have been published wondering if new-borns recognise the mother’s voice. They cannot recognise it because inside the uterus it sounded completely different.