How do babies in the womb breathe?

Babies need oxygen starting early in pregnancy to grow. But the first breath will not be taken by a baby until after birth. This means that in the womb, babies do not even breathe. Instead, the umbilical cord delivers oxygen to the infant before the first respiration.

The formation of the lung starts early in pregnancy, but is not completed until the third trimester. The lungs begin to produce alveoli, tiny lung sacs that fill with oxygen, between 24-36 weeks of pregnancy. A baby will have trouble breathing on its own outside of the womb before these sacs are fully formed.

Often women giving birth worry about how their babies are going to breathe, especially as the baby passes through the narrow confines of the birth canal. The umbilical cord continues to provide oxygen to a baby until after it is born.

Simple facts about how babies breathe in the womb:

  • In the earliest weeks of pregnancy, a developing baby looks more like a ball of cells than a person. In these early weeks, there’s no need to breathe.
  • The umbilical cord is the main source of oxygen for the fetus.
  • As long as the umbilical cord remains intact, there should be no risk of drowning in or outside the womb.

How do babies breathe in the womb?

There is a role played by many biological systems and processes. Included are:

The umbilical cord

New born baby
The umbilical cord provides a baby with oxygen-rich blood in the womb.

The umbilical cord forms after 5-6 weeks of pregnancy to deliver oxygen straight to the body of the developing fetus. The umbilical cord attaches to the uterus-connected placenta. Both structures house several blood vessels, and during pregnancy they continue to expand and develop.

The umbilical cord and placenta together provide nutrients to the baby from the mother. They also provide the baby with the requisite oxygen-rich blood for development.

This implies that for the infant, the mother breathes in, and the oxygen in her blood is then transferred to the blood of the baby. The mother still breathes out for the infant, as the baby’s carbon dioxide is passed from the placenta to the blood of the mother, absorbed with breath.

Substances that enter the developing infant, such as oxygen, never interfere, such as waste materials, with the substances leaving the baby. They pass through two distinct blood vessels through the umbilical cord.

Lung development in the womb

After 35-36 weeks of pregnancy, lung development is usually complete. However, growth varies, and when a baby is born, it is possible to miscalculate. That’s why even late preterm babies sometimes suffer breathing problems. Steroids can help accelerate the development of the lungs of a baby. Doctors may prescribe steroids to the mother when a woman has to give birth early, or when she is at risk of preterm labor, to boost the chances of a baby’s survival outside the womb.

Even when the lungs of a fetus are completely grown, breathing is difficult for the fetus until after birth. Babies that develop are surrounded by amniotic fluid, and this fluid fills their lungs. Developing babies begin to take “practice” breaths by 10-12 weeks of gestation. But these breaths do not provide oxygen for them, and instead replenish the lungs with more amniotic fluid. A fetus can’t drown in the womb because it’s common for the lungs of a fetus to be filled with fluid.

If there is an issue with the placenta or umbilical cord, there’s no other way for a growing baby to breathe. As a consequence, birth defects, brain damage or even the death of the fetus may be caused by complications with these systems.

Breathing during and after birth

Some babies are born with a neck-wrapped umbilical cord. In 12-37 percent of births, this relatively common issue, called the nuchal cord, occurs. It poses no issues in most instances. This is because the umbilical cord is still able to provide oxygen to the baby.

However, if the cord is wrapped around the neck of the baby very tightly, the supply of oxygen in the cord might be reduced. The care professional can look for a nuchal cord during delivery, and unwrap the cord if possible. The new climate, which entails changes in temperature, a lack of amniotic fluid, and exposure to air, causes the first breath of the baby after the baby is born.

During birth, some babies have their first bowel movement before leaving the womb. Meconium is called this stool. A baby may inhale meconium during a practice breath during or shortly prior to birth. Meconium inhalation can be serious and can impair the ability of a baby to breathe outside the womb. So, after birth , babies who have inhaled meconium may need suction and oxygen care.

How water birth affects breathing

A water birth won’t affect a babies ability to breathe.
A water birth won’t affect a babies ability to breathe.

Many hospitals provide water births, which are favoured by some women over conventional birth choices. Women giving birth can also prefer water birth at home or in birthing centers. The birth of water can be soothing, can help alleviate discomfort, and simulate the womb environment. It is normally healthy, and will not impact the ability of a baby to breathe.

This is because the baby will continue to get oxygen from the umbilical cord until the birthing tub is removed. Theoretically, a baby left for too long in the birthing tub could drown. Isolated studies indicate that during water birth, it is common for a baby to be harmed. A 2009 Cochrane study, which looked at 12 previous water birth trials, however, found no rise in the risk of harm to the infant. The baby is brought up and out of the water upon birth and then takes its first breath.

It is worth noting that water distribution is not recommended by both the American College of Obstetricians and Gynecologists and the American Academy of Pediatrics.

Deprivation of oxygen as a birth injury

During and immediately after labor and birth, when a baby does not get enough oxygen, it is called hypoxia. Hypoxia deprives the brain and body of the oxygen that they need to function properly. This can cause a number of incidents at birth, including cerebral paralysis and death. Common causes of hypoxia include:

  • Cord problems, such as a damaged cord, or a cord with damaged blood vessels.
  • Abnormal presentation. Some babies born breech suffer from oxygen deprivation at birth.
  • Shoulder dystocia, which occurs when the shoulders get stuck, slowing delivery after the head has emerged.
  • Excessive bleeding during pregnancy or birth.

The risk of hypoxia can be significantly reduced by adequate maternal care and an attentive care provider throughout birth. A baby suffering hypoxia, such as oxygen therapy or a ventilator, may require supportive treatment.

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