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How Do Babies Breathe in the Womb?

author image Gail Sessoms
Gail Sessoms, a grant writer and nonprofit consultant, writes about nonprofit, small business and personal finance issues. She volunteers as a court-appointed child advocate, has a background in social services and writes about issues important to families. Sessoms holds a Bachelor of Arts degree in liberal studies.
How Do Babies Breathe in the Womb?
Curious what your little one is doing in there? Photo Credit: Halfpoint/iStock/GettyImages

Your unborn baby does not breathe through her mouth and nose while she is in the womb. Birth is the occasion when babies breathe for the first time. Until her exit from the womb, your baby develops in an environment filled with amniotic fluid.

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Unlike your lungs, which expand and contract during breathing, an unborn baby’s lungs are undeveloped, un-inflated and filled with amniotic fluid. Instead, the developing fetus receives all of the benefits of breathing, including oxygen, with help from the mother.

Normal Breathing

Your lungs and circulatory system, which includes your bloodstream, carries oxygen and nutrients to your body and helps remove waste from your body. Normal breathing, inhaling and exhaling, uses the lungs to move oxygenated air to the blood vessels for transport to the bloodstream.

The same systems remove carbon dioxide from the bloodstream and deliver nutrients to the body. Your baby’s circulatory system is still developing while he is in the womb, so the umbilical cord and placenta, which connects baby and mother, do the work normally performed by the lungs.

Breathing Surrogate

The unborn baby exchanges oxygen and carbon dioxide with the mother through the placenta and umbilical cord. The mother’s blood circulates through the placenta and also carries nutrients to the baby. The placenta is attached to the uterine wall and to the umbilical cord, which is attached to the baby.

The mother, in effect, breathes for the baby. The mother inhales and breathes in oxygenated air, which passes through her circulatory system to the baby through the placenta and umbilical cord. Carbon dioxide returns from the baby through the umbilical cord and placenta to the mother, who exhales and removes the waste from her body.

Breathing Practice and Surfactant

Although your unborn baby does not breathe air, she gets breathing practice while in the womb. At about nine weeks into the pregnancy, the fetus begins to engage in movements that resemble breathing. The fetus gets more breathing practice when he occasionally inhales and exhales amniotic fluid near the end of the pregnancy.

Breathing practice prepares the fetus to breathe quickly and effectively after birth. The mother’s body produces surfactant in the amniotic fluid in increasing amounts as the pregnancy continues. The unborn baby needs the surfactant coating on the inside of her lungs to keep the lung’s air sacs open and prevent collapse of the lungs.

First Breath

Your baby takes his first breath when he cries for the first time after birth. Some babies cry on their own, while others need a little help from the doctor or nurses. The newborn baby gasps as he experiences the abrupt change in environment that follows birth. The umbilical cord is cut and the newborn begins to use his lungs.

Now that the baby is breathing on his own, inhaling and exhaling as his lungs inflate and the amniotic fluid drains away, more blood flows to his lungs and blood vessels as oxygen moves through the body and carbon dioxide is expelled.

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