Effect of pregnancy on maternal asthma symptoms and medication use

To examine whether factors related to the patient or her treatment influence asthma severity during pregnancy.

Symptom and medication data were collected by in-person and telephone interviews. Women were recruited before 24 weeks of gestation through private obstetricians and hospital clinics. Eight hundred seventy-two women had physician-diagnosed asthma, 686 were active asthmatics, and 641 with complete data were analyzed. The Global Initiative for Asthma measured severity. Cumulative logistic regression models for repeated measures assessed changes in asthma severity during each month of pregnancy.

Two factors had significant and profound effects on the course of asthma: prepregnancy severity and use of medication according to Global Initiative for Asthma guidelines. Although several factors were analyzed (race, age, atopic status, body mass index, parity, fetal sex, and smoking), none were significant risk factors for changes in asthma severity, measured in a clinically important way as a one-step change in Global Initiative for Asthma category. Women with milder asthma received most benefit from appropriate treatment, 62% decreased risk for worsening asthma among those with intermittent asthma (0.38, 95% confidence interval 0.23-0.64) and 52% decreased risk among those with mild persistent asthma (odds ratio 0.48, 95% confidence interval 0.28-0.84). Month or trimester of gestation was not consistently associated with changes in asthma severity.

Asthma severity during pregnancy is similar to severity in the year before pregnancy, provided patients continue to use their prescribed medication. If women discontinue medication, even mild asthma is likely to become significantly more severe.