Asthma Severity Remains Stable in Pregnant Women Continuing Their Medication

From Medscape Medical News
Laurie Barclay, MD

March 5, 2010 — Asthma severity during pregnancy is similar to severity in the previous year if women continue to take their prescribed medication but is more severe if they discontinue it, according to the results of a study reported in the March issue of Obstetrics & Gynecology.

"Early investigators suggested a rule of thirds: in one third of women, asthma improves during pregnancy; in one third, asthma becomes worse; and in one third it remains the same," write Kathleen Belanger, PhD, from Yale University School of Public Health in New Haven, Connecticut, and colleagues. "However, assessment of improvement has often been subjective, and exacerbations have been measured by hospitalizations and emergency department visits. No studies have used the more common clinical endpoints of symptoms and medication use to assess exacerbation during pregnancy."

The goal of this study was to assess the effect of patient-related or treatment-related factors on asthma severity during pregnancy among women recruited before 24 weeks of gestation through private obstetricians and hospital clinics.
In-person and telephone interviews allowed gathering of symptom and medication data. Of 872 women with physician-diagnosed asthma, 686 had active asthma; of these, 641 women with complete data were analyzed. Changes in asthma severity, measured by the Global Initiative for Asthma, were evaluated during each month of pregnancy with use of cumulative logistic regression models for repeated measures.

Prepregnancy asthma severity and use of medication according to Global Initiative for Asthma guidelines significantly and profoundly affected the course of asthma.
No other factors analyzed were significant risk factors for clinically meaningful changes in asthma severity, defined as a 1-step change in the Global Initiative for Asthma category. These included race, age, atopic status, body mass index (BMI), parity, fetal sex, and smoking.

The most benefit from appropriate treatment was observed in women with milder asthma, with a 62% decreased risk for worsening asthma among those with intermittent asthma (odds ratio [OR], 0.38; 95% confidence interval [CI], 0.23 - 0.64) and a 52% decreased risk among those with mild persistent asthma (OR, 0.48; 95% CI, 0.28 - 0.84). The gestational month or trimester 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," the study authors write.
"If women discontinue medication, even mild asthma is likely to become significantly more severe."

Limitations of this study include failure to directly measure lung function; and collection of symptom and medication data by interview, which could result in recall errors.

"Recent research indicates that the fetus may experience significant risk from exacerbations of asthma in the mother," the study authors conclude.
"The American College of Obstetricians and Gynecologists (the College) recommends continuation of medication for the health of both mother and fetus. The current paper provides empirical support for the College guidelines: exacerbations during pregnancy are best prevented when the mother uses asthma medication appropriate to her level of symptoms."

The National Institutes of Health supported this study. The study authors have disclosed no relevant financial relationships.

Obstet Gynecol. 2010;115:559-567. Abstract