Babies don’t breathe in the womb as we understand “breathing.” Instead, babies rely on their birthing parent’s breathing to receive oxygen in their developing organs.

After 9 months of growing inside a pregnant person’s body, a baby undergoes a complicated physical transition as they exit the womb. Research shows this transition is one of the most intricate things the body does.

While babies “practice” breathing in utero, they don’t use their lungs for breathing until they take their first breath outside the womb.

The placenta and umbilical cord are organs that enable a developing baby to get everything they need from their birthing parent. This includes oxygen.

Every breath that the birthing parent takes brings oxygen into the birthing parent’s bloodstream and sends that oxygen-rich blood through the placenta to the baby through the umbilical cord.

During weeks 10 and 11 of pregnancy, the developing baby inhales tiny bits of amniotic fluid. This “inhalation” is more like a swallowing movement. It helps the baby’s lungs as they begin to develop.

By week 32 of pregnancy, a baby practices more “breath-like” movements involving compression and expansion of the lungs.

Even though the baby’s lungs do not fully develop at 32 weeks, there is a good chance a baby born at this stage might survive outside the womb.

In fact, there are times when it is medically indicated for a fetus to be born at 32 weeks. If there is a planned premature delivery, then the fetus may receive betamethasone or a steroid injection that helps induce fetal lung maturity.

The breathing practice is a developmental milestone that sets the new baby up for success during their first cry. Healthcare professionals consider the baby’s lungs mature at 36 weeks. By then, a baby completes at least 4 weeks of breathing practice.

Around the 40-week mark of pregnancy, the baby’s ready to transition out of the womb and into the world. During labor, the birthing parent’s uterus contracts and retracts. The movements cause the birthing parent to feel intense sensations, signaling that the baby’s about to arrive.

The contractions squeeze the baby, moving them into position to exit the birth canal. The contractions also serve to push amniotic fluid out of the baby’s lungs, preparing them to breathe.

The seal between the baby and the outside world breaks when the birthing parent’s water breaks. The baby may get exposure to oxygen during the birth process. But while the baby remains connected to their birthing parent through the placenta via the umbilical cord, the baby doesn’t have to breathe on their own.

Within a few moments after birth, the baby takes a sharp inhale and breathe for the first time on their own. This inflation of the lungs brings oxygen into the baby’s bloodstream without the birthing parent’s help for the first time.

The baby’s new lungs are likely ready to carry them through life. But the respiratory system still needs to develop. Alveoli are tiny air sacs in the lungs that enable the exchange of oxygen in our bodies. They will continue to develop after birth.

At birth, experts estimate that most babies have between 24 million alveoli in their lungs. By the time a child turns 8 years old, they have up to 280 million.

As the lungs grow, alveoli populate the new surface area of the lungs. This enables the lungs to support a growing human as they need increasing amounts of oxygen.

The bones of the rib cage encircle our vital organs. As a baby grows, these bones grow harder and the lungs become more secure. This is an important part of respiratory development.

When we are first born, we are extremely vulnerable to “having the wind knocked out of us” because of the softness of our rib cages. But the ribs also rise in the chest to take an adult shape.

Sometimes a baby involuntarily swallows or inhales parts of their first bowel movement during birth. This first bowel movement is called the meconium.

When a baby swallows or inhales the meconium, it’s essential to remove the baby from the womb quickly and get them medical attention. If healthcare professionals do not remove the meconium, it can pollute the baby’s delicate lungs.

These babies usually survive and do just fine, because many of them end up admitted to the neonatal ICU for further resuscitative measures.

One of the common complications of having a premature birth is that the baby’s lungs cannot fully mature. Pneumonia and a condition called respiratory distress syndrome can result. One way to avoid a premature birth is to pay careful attention to your diet, exercise, and other lifestyle choices during pregnancy.

It’s important for pregnant people to avoid:

  • raw meat
  • sushi
  • deli meat
  • uncooked eggs

All the above foods contain harmful chemical agents or bacteria that can lead to health concerns for a baby during development. Experts recommend that pregnant people try to limit their intake of caffeine, and avoid alcoholic beverages.

The FDA keeps an ongoing registry of medications that are safe to take during pregnancy. If one of your prescription medications is on the list of unsafe medications, speak with your doctor about the risks of continuing to use it.

You developing baby does not breathe in the same way that we do. Fresh oxygen is delivered to them along with their essential nutrients from the placenta. As their lungs form, they begin to expand and contract and are considered to be fully developed around 36 weeks.

Breathing as we know it starts with a baby’s first cry at birth.