Have you ever wondered how babies receive oxygen while still in the womb? Although some people are familiar with this process, others may not have considered how it works. The way babies receive oxygen before birth is both fascinating and complex.
Babies Do Not Breathe in the Womb
Unlike fish, which use gills to extract oxygen from water, human fetuses do not breathe in amniotic fluid. Instead, oxygen is delivered to the fetus via the placenta, which is connected to the fetus by the umbilical cord. When a pregnant person inhales oxygen, it enters their bloodstream, passes through the placenta, and is transported to the fetus through the umbilical cord (Moore et al., 2020).
Although fetal lungs begin to develop around 9 to 11 weeks of gestation, they are not used for breathing air during pregnancy. Instead, fetuses perform fetal breathing movements (FBMs)—a practice of inhaling and exhaling small amounts of amniotic fluid. These movements help the lungs mature and prepare for postnatal breathing (Harding, 2001).
By approximately 32 weeks gestation, FBMs become more regular and coordinated. By 37 to 39 weeks, most fetuses have developed lungs capable of producing enough surfactant—a substance that prevents the lungs from collapsing—to support breathing outside the womb (Jobe & Ikegami, 2000).
How Do Babies Transition to Breathing Air?
During labor, uterine contractions help expel fluid from the fetus’s lungs. At birth, the baby experiences a dramatic shift in environment—temperature, pressure, and exposure to air—which stimulates the body to take its first breath.
Contrary to popular belief, a newborn’s first breath is not caused by cutting the umbilical cord. Instead, the transition begins when exposure to air and elevated carbon dioxide levels stimulate the brain’s respiratory center (Hillman et al., 2012).
Key Points About the Transition to Breathing
- Ongoing Oxygen via the Umbilical Cord: After birth, the baby remains connected to the umbilical cord for a short time, continuing to receive oxygen until independent breathing is fully established.
- Delayed Cord Clamping: Waiting at least 30 to 60 seconds before clamping the cord is recommended. This allows additional oxygen-rich blood to transfer from the placenta to the baby, lowering the risk of anemia and other complications (Rabe et al., 2019).
- Water Births and the Dive Reflex: In water births, babies do not breathe underwater. A natural reflex known as the dive reflex prevents inhalation until the newborn senses air on the skin (Johnson, 2018).
The Remarkable Process of Birth
Once the newborn takes its first breath, the lungs expand, and the body shifts from receiving oxygen via the placenta to breathing independently. This marks the final stage of transition from intrauterine to extrauterine life.
Understanding how oxygen exchange occurs before birth highlights the incredible complexity of fetal development. From the placenta’s vital role to the newborn’s first breath, each step is a testament to the extraordinary design of human life.
References
Harding, R. (2001). Fetal breathing movements. The Journal of Physiology, 535(1), 1–15. https://doi.org/10.1111/j.1469-7793.2001.t01-1-00001.x
Hillman, N. H., Kallapur, S. G., & Jobe, A. H. (2012). Physiology of transition from intrauterine to extrauterine life. Clinics in Perinatology, 39(4), 769–783. https://doi.org/10.1016/j.clp.2012.09.009
Jobe, A. H., & Ikegami, M. (2000). Lung development and function after surfactant treatment. Pediatrics, 106(6), 1293–1296. https://doi.org/10.1542/peds.106.6.1293
Johnson, P. (2018). Water birth: The science behind the practice. Midwifery Today, 126, 38–40.
Moore, K. L., Persaud, T. V. N., & Torchia, M. G. (2020). The developing human: Clinically oriented embryology (11th ed.). Elsevier.
Rabe, H., Gyte, G. M., Díaz-Rossello, J. L., & Duley, L. (2019). Effect of timing of umbilical cord clamping and other strategies to influence placental transfusion at preterm birth on maternal and infant outcomes. Cochrane Database of Systematic Reviews, 9(CD003248). https://doi.org/10.1002/14651858.CD003248.pub4
