Asthma control during pregnancy and the risk of preterm delivery or impaired fetal growth

Concerns regarding potential harmful effect of medications on fetuses often result in inadequate treatment of asthma in pregnancy, whereas risks posed by poorly controlled maternal asthma are often underestimated.

To evaluate the effect of maternal asthma on preterm delivery and fetal growth.

Study participants were individuals enrolled in the Organization of Teratology Information Specialists Asthma Medications in Pregnancy Study between February 1, 1998, and December 31, 2003. Pregnant women with physician-diagnosed asthma (n = 719) evaluated their asthma control repeatedly during pregnancy based on symptom frequency and interference with daily activities and sleep and reported hospitalizations and unscheduled clinic visits for asthma exacerbations. The incidence of preterm delivery, the incidence of intrauterine growth restriction, and mean birth weight were evaluated relative to asthma symptom control and exacerbation measures.

The incidence of preterm delivery was significantly higher among patients with inadequate asthma symptom control during the first part of pregnancy (11.4%) compared with patients with adequate asthma control (6.3%; P = .02). Similarly, patients who were hospitalized for asthma during pregnancy had a higher incidence of preterm delivery (16.4%) compared with asthmatic women without a history of hospitalization (7.6%; P = .02). The effect seemed independent from use of systemic corticosteroids and other covariates. Neither the incidence of intrauterine growth restriction nor mean birth weight varied by any measures of asthma symptom control or exacerbations.

This study demonstrates a substantial risk for preterm delivery posed by poorly controlled maternal asthma and provides additional evidence regarding the importance of adequate treatment of asthma in pregnancy to maintain optimal asthma control.