Breathlessness in Pregnancy: What Causes It?

We all experience breathlessness when we tire ourselves during strenuous physical activity. Some people can go for longer before breathlessness sets in. It depends on individual level of physical conditioning. However, when breathlessness arises with minor physical activity, or even at rest then it is a cause for concern. At this point it is referred to as dyspnea, a broad medical term for difficult breathing. Dyspnea may sound serious and it can be but sometimes it caused by relatively minor conditions.

Shortness of Breath in Pregnancy

Pregnancy is probably the only time in life when mild breathlessness with even slight physical activity may be considered somewhat normal. However, this does not mean that it cannot be serious. It largely depends on the circumstances. Many pregnant women will find that they may experience mild breathless from the second trimester onwards and it tends to worsen by the third trimester.

It does not afflict every pregnant woman. For some women it will only arise after quickly climbing up a flight of stairs, while for others it may arise with a short walk to the kitchen. However, breathlessness that does not ease with rest of change in position, which causes paleness of the skin or a bluish tinge and is accompanied by dizziness or fainting is very serious even in pregnant women.

Causes of Pregnancy-Related Breathlessness


Iron-deficiency anemia is one of the most common causes of breathlessness in pregnancy. About 1 out 10 women of reproductive age suffer with iron-deficiency anemia. Therefore the anemia may often be pre-existing even before conception but the pregnant state just worsens it. Other women develop iron-deficiency anemia during the course of pregnancy, usually by the third trimester but sometimes earlier by the second trimester. Other types of anemia can also lead to breathlessness during pregnancy.

The demands of the growing fetus can quickly deplete the mother’s iron stores if it was insufficient and dietary intake of iron was not adequate. The lower hemoglobin level in iron-deficiency anemia means that the blood does not have the same oxygen-carrying capacity. In mild cases it only becomes evident as breathlessness with physical activity. This occurs because the body demands more oxygen during physical activity but the blood cannot deliver the required oxygen. The heart tries to work harder and breathing rate increases.

Enlarged Uterus

The growing uterus can impair the action of breathing muscles. The diaphragm which is the main respiratory muscle normally flattens and pushes the abdominal contents slightly downwards during inhalation. However, this is impeded to some extent with the enlarged uterus. Even the abdominal muscles which sometimes aids with respiration cannot work as effectively as it normally would during pregnancy, particularly in late pregnancy when the abdominal muscles are stretched.

The other aspect with the enlarged uterus is that it can press against the large artery and vein that lead out of and back to the heart. It can then affect the heart’s function to receive oxygen-deficient blood and push out oxygen-rich blood. This can strain the heart and limit the distribution of oxygen throughout the body. The effect is more pronounced when a pregnancy women lies flat on her back. Lying on the side or sitting upright can often help ease the strain.

Other Causes

Apart from the two reasons mentioned above, there are also other reasons why breathlessness may occur in pregnancy. Many of the following conditions are not dependent on the pregnant state. It can occur even without pregnancy and also affect men.

  • Anxiety
  • Bronchitis
  • Chronic obstructive pulmonary disease (COPD)
  • Heart failure
  • Pneumonia
  • Shock

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