Asthma is the most common, potentially serious medical condition to complicate pregnancy. In fact, asthma affects almost 7 percent of women in their childbearing years. Well-controlled asthma is not associated with significant risk to mother or fetus. Although uncontrolled asthma is rarely fatal, it can cause serious maternal complications including high blood pressure, toxemia and premature delivery. Fetal complications of uncontrolled asthma include increased risk of stillbirth, fetal growth retardation, premature birth, low birth weight and a low Apgar score at birth. 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 spontaneous abortion or congenital 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.
What is asthma and what are its symptoms?
Asthma is a condition characterized by obstruction in the airways of the lungs caused by spasm of surrounding muscles, accumulation of mucus, and swelling of the airway walls due to the gathering of inflammatory cells. Unlike individuals with emphysema who have irreversible destruction of their lung cells, asthmatic patients usually have a condition that can be reversed with vigorous treatment.
Individuals with asthma most often describe what they feel in their airways as a “tightness.” They also describe wheezing, shortness of breath, chest pain, and cough. Symptoms of asthma can be triggered by allergens (including pollen, mold, animals, feathers, house dust mites and cockroaches), environmental factors, exercise, infections and stress.
What are the effects of pregnancy on asthma?
When women with asthma become pregnant, a 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:
- Women with severe asthma are more likely to worsen, while those with mild asthma are more likely to improve.
- The change in the course of asthma in an individual woman during pregnancy tends to be similar on successive pregnancies.
- Asthma exacerbations are most likely to appear during the weeks 24 to 36 of gestation, with only occasional patients (10 percent or fewer) becoming symptomatic during labor and delivery.
- The changes in asthma noted during pregnancy usually return to pre-pregnancy status within three months of delivery.
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. These events may be confused with or add to allergic or other triggers of asthma. 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.
For pregnant women with asthma, the type and frequency of fetal evaluation is based on gestational age and maternal risk factors. Sonography (ultrasound) can be performed before 12 weeks if there is concern about the accuracy of an estimated due date and repeated later if a slowing of fetal growth is suspected. Electronic heart rate monitoring, called “non-stress testing” or “contraction stress testing,” and ultrasonic determinations in the third trimester may be used to assess fetal well being. For third trimester patients with significant asthma symptoms, the frequency of fetal assessment should be increased if problems are suspected. Asthma patients should record fetal activity or kick counts daily to help monitor their baby according to their physician’s instructions.
During a severe asthma attack in which symptoms do not quickly improve, there is risk for significant maternal hypoxemia, a low oxygen state. This is an important time for fetal assessment; continuous electronic fetal heart rate monitoring may be necessary along with measurements of the mother’s lung function.
Fortunately during labor and delivery, the majority of asthma patients do well, although careful fetal monitoring remains very important. In low risk patients whose asthma is well-controlled, fetal assessment can be accomplished by 20 minutes of electronic monitoring (the admission test). Intensive fetal monitoring with careful observation is recommended for patients who enter labor and delivery with severe asthma, have a non-reassuring admission test or other risk factors.
Avoidance and control
The connection between asthma and allergies is common. Most asthmatic patients (75 to 85 percent) will test allergic to one or more allergens such as: pollens, molds, animals, feathers, house dust mites and cockroaches. Pet allergies are caused by protein found in animal dander, urine and saliva. These allergens may trigger asthma symptoms or make existing symptoms worse.
Other non-allergic substances may also worsen asthma and allergies. These include tobacco smoke, paint and chemical fumes, strong odors, environmental pollutants (including ozone and smog) and drugs, such as aspirin or beta-blockers (used to treat high blood pressure, migraine headache and heart disorders).
Avoidance of specific triggers should lessen the frequency and intensity of asthmatic and allergic symptoms. Allergists-immunologists recommend the following methods:
- Remove allergy causing pets or feather pillows/comforters from the house.
- Seal pillows, mattresses and box springs in special dust mite-proof casings (your allergist should be able to give you information regarding comfortable cases).
- Wash bedding weekly in 130 degree F. water (comforters may be dry-cleaned periodically) to kill dust mites.
- Keep home humidity under 50 percent to control dust mite and mold growth.
- Use filtering vacuums or “filter vacuum bags” to control airborne dust when cleaning.
- Close windows, use air-conditioning and avoid outdoor activity between 5 and 10 a.m. when pollen and pollution are at their highest.
- Avoid chemical fumes and, most importantly, tobacco smoke.