The developing baby inside the womb is constantly active, practicing skills necessary for life outside the uterus. These movements often lead to speculation about whether they perform actions like yawning, crying, or even coughing. While a fetus engages in many preparatory movements, the physical environment of the womb dictates which actions are truly possible. The answer to whether a baby can cough is complex, depending on the distinction between a reflex and a mechanical action.
Why a True Cough is Not Possible
A true cough is a forced expulsion of air from the lungs, a protective reflex meant to clear the airway of irritants or foreign material. This mechanism is physiologically impossible for a fetus developing in utero. The reason lies in the composition of the fetal lungs, which are not filled with air but with fetal lung liquid.
This liquid is secreted by the lung tissue itself and plays a major role in the proper growth and development of the lung structure. Since the lungs are a liquid-filled organ, there is no air to rapidly and forcefully expel, which is the foundational action of a cough. The fetus receives all necessary oxygen through the umbilical cord and the placenta, meaning the lungs do not yet function for gas exchange.
The liquid environment prevents the creation of the high-pressure burst of air that defines a cough. Any attempt at a forceful exhalation would only result in a slight displacement of the viscous fluid. The airway is protected by the continuous fluid environment itself, which washes away potential debris.
Movements That Feel Like a Cough
Many pregnant people report feeling a sudden, jerky movement that they interpret as a cough or a hiccup; the latter is far more common. Fetal hiccups are frequently felt rhythmic movements in the womb, often beginning in the second trimester and becoming more pronounced in the third.
These hiccups are caused by involuntary spasms of the developing diaphragm muscle, which is practicing for its eventual role in breathing. When the fetus inhales amniotic fluid, the diaphragm contracts against the fluid, resulting in a sudden, repetitive motion. This motion is felt by the mother as a consistent, pulsating jump that lasts for a short period.
Another common activity is Fetal Breathing Movements (FBMs), which are practice movements of the diaphragm and chest muscles. These movements are typically more shallow and irregular than hiccups and increase in frequency as the pregnancy progresses, especially between 26 and 32 weeks of gestation. Both FBMs and hiccups serve as practice for the muscles used for respiration after birth.
When the Cough Reflex Fully Develops
While the fetus cannot perform the physical action of a cough, the neurological pathways for airway protection are developing. The primary protective response in the newborn is the laryngeal chemoreflex (LCR), triggered by fluid near the larynx.
The LCR typically manifests as apnea (a pause in breathing), swallowing, and closure of the larynx to prevent aspiration. The true, mature cough reflex, which forcefully clears the airway, is often not fully functional immediately at birth. The transition to air-breathing triggers the clearance of the fetal lung liquid.
The ability to produce a strong, protective cough develops gradually over the first few months after delivery. Studies suggest the cough reflex becomes a more prominent response to airway stimulation, replacing the LCR components, typically around one to two months of age.