This lesson focuses on the remarkable physiology that keeps babies safe during birth by preventing premature breathing in the womb. Barbara Harper introduces the three natural fetal breathing inhibitors—decreased fetal breathing movements, high pulmonary vascular resistance, and mild hypoxia—and explains how each plays a protective role throughout labor and delivery.

We begin by examining fetal breathing movements (FBM), which are essential for lung development but gradually slow and then stop by 4 cm dilation. This pause, driven by rising levels of prostaglandin E2, helps conserve oxygen as labor intensifies. The lesson then explores the unique circulatory system of the fetus, where pulmonary resistance remains high until after birth. Only once the lungs are perfused with oxygenated blood—while the umbilical cord is still attached—can true respiration begin.

Through real-world data, Barbara explains how mild hypoxia is not only expected but necessary in the moments after birth. This temporary low oxygen state activates vital reflexes, including the first instinct to swallow before breathing begins. We also explore the dive reflex, a powerful safety mechanism triggered by chemoreceptors in the larynx that protects newborns from aspirating fluid.

Supported by current research and clinical insight, this lesson provides a deeper understanding of fetal adaptation and the critical transition from womb to world. Providers gain the tools to educate families and advocate for evidence-based practices—like delayed cord clamping—that honor the body’s innate wisdom and enhance neonatal safety during waterbirth.