The effect of pregnancy on asthma varies. Worsening of the disease is slightly more common than improvement, but most pregnant women do not have severe asthma attacks.
(See also Asthma Asthma Asthma is a condition in which the airways narrow—usually reversibly—in response to certain stimuli. Coughing, wheezing, and shortness of breath that occur in response to specific triggers are... read more 
.)
The effect of asthma on pregnancy also varies. But if asthma is severe and poorly controlled, it increases the risk of having the following:
Preeclampsia Preeclampsia and Eclampsia Preeclampsia is new high blood pressure or worsening of existing high blood pressure that is accompanied by excess protein in the urine and that develops after the 20th week of pregnancy. Eclampsia... read more (a type of high blood pressure that occurs during pregnancy)
A fetus that may not grow as much as expected (small for gestational age Small-for-Gestational-Age (SGA) Newborn A newborn who weighs less than 90% of newborns of the same gestational age at birth (below the 10th percentile) is considered small for gestational age. Newborns may be small because their parents... read more )
Complications in pregnant women, including death
Treatment of Asthma During Pregnancy
Inhaled bronchodilators and corticosteroids
Because asthma can change during pregnancy, doctors may ask women with asthma to use a peak flow meter to monitor their breathing more often. Pregnant women with asthma should see their doctor regularly so that treatment can be adjusted as needed. Maintaining good control of asthma is important. Inadequate treatment can result in serious problems.
Inhaled bronchodilators (such as albuterol) and inhaled corticosteroids (such as budesonide) can be used during pregnancy. When inhaled, the drugs affect mainly the lungs and are less likely to affect the whole body and the fetus than when they are taken by mouth. Theophylline (taken by mouth) is not usually used during pregnancy.
Corticosteroids taken by mouth are used only when other treatments are ineffective. If asthma suddenly worsens, women are given a corticosteroid intravenously for 24 to 48 hours, then by mouth.
Being vaccinated against the influenza (flu) virus during the flu season is particularly important for pregnant women with asthma.
