How does the baby hold its breath when it’s born into the water?

How does the baby hold its breath when it’s born into the water?

September 29, 2022

With 14 years of experience as a birth educator I have answered this question a fair bit.  

The short answer is: They don’t hold their breath, because they haven’t taken a breath yet.

Which is a very simple answer to a very complex phenomenon.

The detailed answer is…

From about 10 weeks gestation babies will begin practicing their breathing, this helps their lungs, diaphragm, and chest muscles prepare for breathing at birth.  But even though babies practice breathing for most of their time in utero, they aren’t actually breathing air / oxygen into their lungs during their practice, because there is no air; they are surrounded by amniotic fluid.  During pregnancy babies receive all their oxygen in the form of oxygenated blood that travels from the placenta, into the baby’s body, via the umbilical cord.  

About 2 days before labour begins naturally, the baby’s breathing practice will stop.  Research suggests that it is probably because of a surge in a hormone called Prostaglandin E2.

When baby is born into the water, as long as the cord remains un-clamped and un-cut, the baby will still be receiving warm oxygenated blood just as they were during pregnancy.  Leaving the cord un-clamped and un-cut also helps to maintain baby’s body temperature because they are still receiving heat from blood circulating between the mother’s body and their own.

Your internal body temperature is about 37 degrees, and the ideal temperature of your birth pool water is about 37 degrees, this is why your midwife will keep an eye on the temperature of your birth pool water when birth is imminent.  When your baby is born into water which is similar in temperature and pressure to the ‘water’ they came from inside your body, they aren’t triggered to take a breath, and the lungs stay deflated as they were in utero.

Baby won’t try to take a breath until they are lifted to the surface of the water and their face comes in contact with the cooler temperature and lower pressure of the air.  It takes air for breath, so when baby is brought to the surface and its face hits the air, your baby will take their first breath.

Another factor that inhibits babies from trying to breathe under water is the Dive Reflex. The Dive Reflex causes the larynx to close over when water passes over it.  This causes the water to be swallowed into the stomach, rather than inhaled into the lungs. This process is further supported by the large number of taste buds found around the larynx (The larynx has five times as many as taste buds as the whole surface of the tongue) which is thought to help the baby determine what can be inhaled and what should be swallowed.  

Even if water was to travel past the larynx, it could not pass into the lungs because amniotic fluid is a hypertonic solution, and is more dense than water. 

Most midwives will support / encourage women to use water as a form of relaxation and pain relief during labour, and if mum and baby are well, it is safe for baby to be born into the water.

There are some circumstances where giving birth into the water isn’t recommended, so if you or your baby have any known health concerns, please discuss water birth with your midwife to decide whether birthing into the water is right for you.  If not, you may well be able to enjoy the benefits of labouring in water, before getting out of the pool to birth your baby.