Shortness of breath (dyspnea) is a widely reported symptom during pregnancy, often described as being unable to take a satisfying deep breath or feeling winded after minimal effort. Estimates suggest that between 60% and 70% of pregnant individuals experience dyspnea at some point. While this sensation can be alarming, it is usually a normal and harmless physiological adaptation. The perception of breathlessness typically occurs without a drop in actual oxygen levels, meaning the fetus remains well-oxygenated throughout.
The Pregnancy Timeline for Breathing Changes
The onset of breathlessness follows a general timeline with two distinct phases. The first phase can begin very early, often within the first trimester, driven primarily by hormonal changes before the uterus has significantly enlarged. Roughly half of pregnant individuals report experiencing dyspnea by the 20th week of gestation.
The second, and often more noticeable, phase occurs later, typically increasing in frequency and intensity throughout the second and third trimesters. By the third trimester (around weeks 31 to 34), the growing uterus pushes upward, leading to a mechanical restriction that makes deep breaths more difficult. This later phase usually continues until the baby “drops” lower into the pelvis—a process called lightening—which often happens a few weeks before delivery, offering relief.
The Underlying Physiological Reasons
Breathlessness results from a combination of hormonal signals and physical changes. The most important hormonal factor is the surge in progesterone, which acts as a powerful respiratory stimulant. Progesterone influences the brain’s respiratory center, increasing minute ventilation—the total volume of air breathed per minute—by increasing the tidal volume (air inhaled with each breath) by 30% to 40%.
This increased ventilation efficiently eliminates carbon dioxide, maintaining a chemical balance that facilitates oxygen transfer to the fetus. Although beneficial for the baby, this frequent, deeper breathing pattern is perceived by the mother as being out of breath.
In addition to hormonal changes, the expanding uterus physically displaces the diaphragm. Upward pressure can elevate the diaphragm by as much as 4 centimeters by the third trimester. This mechanical restriction reduces the functional residual capacity of the lungs (air remaining after a normal exhale) by 10% to 25%. This reduction in lung volume makes it difficult to take a full, satisfying breath, especially during physical activity.
Strategies for Improving Breathing Comfort
While the causes of physiological dyspnea are unavoidable, several simple changes can help manage the daily discomfort.
Posture and Rest
Maintaining good posture is effective, as sitting or standing up straight maximizes the space available for the lungs to expand. Slouching compresses the chest cavity, intensifying breathlessness. When resting or sleeping, prop the upper body up with several pillows into a semi-sitting position; this uses gravity to pull the uterus away from the diaphragm.
Activity and Positioning
Pace physical activity and slow down immediately when breathlessness occurs. After 20 weeks of gestation, avoid the supine position (lying flat on the back) to prevent the uterus from compressing major blood vessels and restricting breathing. Lying on the left side with the head slightly elevated is recommended to optimize circulation and respiratory comfort. Simple breathing exercises focusing on slow, deep chest breaths can also help a person feel more in control.
Identifying Warning Signs and When to Call a Doctor
While most shortness of breath in pregnancy is normal, certain symptoms indicate a need for immediate medical attention, suggesting underlying conditions like anemia, pulmonary embolism, or heart issues. Contact a healthcare provider if the breathlessness is constant, suddenly worsens, or does not improve with rest. A doctor may check for anemia, which reduces oxygen-carrying red blood cells, by ordering a blood test.
Call emergency services immediately if the shortness of breath is severe or accompanied by other serious symptoms. If you have a pre-existing condition like asthma, any significant increase in symptoms or need for rescue inhaler use should also prompt a call to your doctor. High-risk symptoms suggesting a lack of adequate oxygen include:
- Sharp chest pain
- A rapid or racing heart rate
- Feeling faint or dizzy
- Coughing up blood
- Wheezing
- Blue discoloration of the lips, fingers, or toes