Babies practice breathing in the womb through fetal breathing movements (FBMs). This “breathing” differs from postnatal breathing; instead of air, the fetus moves amniotic fluid within its developing respiratory system. This activity is crucial for preparing the baby’s lungs and muscles for life outside the womb.
Understanding Fetal Breathing Movements
Fetal breathing movements involve rhythmic contractions of the diaphragm and other chest muscles, similar to postnatal breathing. These movements occur in a fluid-filled environment, with the fetus moving amniotic fluid in and out of its lungs. This practice is not for oxygen exchange, as the baby receives all necessary oxygen through the umbilical cord and placenta.
The diaphragm, a muscle separating the chest cavity from the abdomen, plays a primary role in these movements. These chest wall and abdominal movements are precursors to breathing air and do not result in gas exchange within the lungs. The presence of amniotic fluid within the lungs is normal and necessary for proper lung development.
Why Babies Practice Breathing
Fetal breathing movements prepare the respiratory system for independent function after birth. These practice sessions strengthen the baby’s respiratory muscles, including the diaphragm, essential for taking the first breaths of air. The movements also promote the development and maturation of lung tissue.
The movement of amniotic fluid in and out of the lungs is crucial for the formation of tiny air sacs called alveoli. These alveoli are where oxygen and carbon dioxide will be exchanged with the blood after birth. FBMs also contribute to maintaining lung expansion, essential for the structural maturation and growth of the fetal lungs.
Development of Practice Breathing
Fetal breathing movements typically begin early in pregnancy, observed as early as 10 to 11 weeks of gestation. They become more regular and pronounced as pregnancy advances, particularly after 28 weeks. These movements are not continuous; they occur in episodes, often linked to the baby’s sleep-wake cycles.
For instance, at 24 to 28 weeks, a fetus might spend about 10 to 20 percent of the time practicing breathing, increasing to 30 to 40 percent after 30 weeks. Neurological control involves the central nervous system, with electrical activity observed in the fetal diaphragm early in development. The frequency and intensity of these movements increase throughout gestation.
Breathing After Birth
A physiological transition occurs at birth as the baby prepares for independent breathing. Until this point, the umbilical cord and placenta have provided all necessary oxygen. During labor, uterine contractions can help squeeze amniotic fluid out of the baby’s lungs, preparing them for air.
Within approximately 10 seconds of delivery, a newborn typically takes its first breath, often sounding like a gasp. This initial breath inflates the lungs, previously filled with fluid. The fluid then drains or is absorbed, allowing the lungs to begin taking in oxygen and expelling carbon dioxide independently. This transition also involves significant changes in the baby’s circulatory system, redirecting blood flow to the newly functioning lungs.