Asthma is the most common potentially serious medical condition to complicate pregnancy.
Asthma can be controlled by careful medical management and avoidance of known triggers, so asthma need not be a reason for avoiding pregnancy. Most measures used to control asthma are not harmful to the developing fetus and do not appear to contribute to either miscarriage or birth defects.
Although the outcome of any pregnancy can never be guaranteed, most women with asthma and allergies do well with proper medical management by physicians familiar with these disorders and the changes that occur during pregnancy.
When women with asthma become pregnant, one-third of the patients improve, one-third worsen, and the last third remain unchanged. Although studies vary widely on the overall effect of pregnancy on asthma, several reviews find the following similar trends:
Pregnancy may affect asthmatic patients in several ways. Hormonal changes that occur during pregnancy may affect both the nose and sinuses, as well as the lungs. An increase in the hormone estrogen contributes to congestion of the capillaries (tiny blood vessels) in the lining of the nose, which in turn leads to a “stuffy” nose in pregnancy (especially during the third trimester). A rise in progesterone causes increased respiratory drive, and a feeling of shortness of breath may be experienced as a result of this hormonal increase. Spirometry and peak flow are measurements of airflow obstruction (a marker of asthma) that help your physician determine if asthma is the cause of shortness of breath during pregnancy.