Background: The use of administrative databases to perform epidemiological studies in asthma has increased in recent years. The absence of clinical parameters to measure the level of asthma severity and control is a major limitation of database studies. A study was undertaken to develop and validate two database indexes to measure the control and severity of asthma. Methods: Database indexes of asthma severity and control were derived from definitions in the Canadian Asthma Consensus Guidelines based on dispensed prescriptions and on medical services recorded in two large administrative databases from the Canadian province of Québec (Régie de l'Assurance Maladie du Québec (RAMQ) and MED-ECHO) over 12 months. The database indexes of asthma severity and control were validated against the pulmonary function test results of 71 patients with asthma randomly selected from two asthma clinics, and they were also applied to a cohort of patients with asthma followed up for 139 283 person-years selected from the RAMQ and MED-ECHO databases between 1 January 1997 and 31 December 2004. Results: According to the database indexes, 49.3%, 29.6% and 21.1% of patients recruited at the asthma clinics were found to have mild, moderate and severe asthma, respectively, while 53.5% were found to have controlled asthma. The mean predicted value of the forced expiratory volume in 1 s (FEV 1 ) ranged from 89.8% for mild asthma to 61.5% for severe asthma (p,0.001), whereas the range from controlled to uncontrolled asthma was 89.5% to 67.3% (p,0.001). The ratio of the FEV 1 to the forced vital capacity (FEV 1 / FVC ratio) measured in 56 patients ranged from 75.8% for mild asthma to 61.8% for severe asthma (p = 0.030), whereas the range from controlled to uncontrolled asthma was 75.3% to 65.7% (p,0.001). Conclusion: In the absence of clinical data, these database indexes could be used in epidemiological studies to assess the severity and control of asthma.

Mothers with severe and moderate asthma during pregnancy have a higher risk of SGA babies than those with mild asthma.

There are conflicting results concerning the impact of maternal asthma during pregnancy on perinatal outcomes. The present study investigated the associations between maternal asthma during pregnancy and the risk of a small-for-gestational-age (SGA) infant, a low-birth-weight (LBW) infant, and preterm birth. A population-based cohort of 40,788 pregnancies from asthmatic and non-asthmatic women was reconstructed through the linking of three Quebec (Canada) administrative databases between 1990 and 2002. A two-stage sampling cohort design was used to collect additional information by way of a mailed questionnaire. The generalized estimation equation models were used to obtain adjusted odds ratios of SGA, LBW and preterm birth comparing asthmatic and non-asthmatic women. The cohort included 13,007 pregnancies from asthmatic and 27,781 pregnancies from non-asthmatic women. Final estimates showed that the odds of SGA (odds ratio: 1.27, 95% confidence interval: 1.14, 1.41), LBW (1.41: 1.22, 1.63) and preterm delivery (1.64: 1.46, 1.83) were significantly higher among asthmatic than non-asthmatic women. Mothers with asthma during pregnancy are more likely to have SGA, LBW, or preterm birth infants than non-asthmatic women. These results can be more easily generalized to women with lower socio-economic status since the cohort under represents women with high socio-economic status.

Recent studies have found that asthmatic women pregnant with a female fetus reported more symptoms and had slightly lower lung function than women pregnant with a male fetus. In order to further investigate this association, we studied the effect of fetal sex on maternal asthma exacerbations and the use of asthma medications during pregnancy. A large cohort of pregnant asthmatic women and their babies was reconstructed between 1990 and 2002 from the linkage of three administrative databases of the Canadian province of Quebec. Asthma exacerbations were defined as a filled prescription of oral corticosteroids, an emergency department visit, or a hospitalization for asthma. Women pregnant with a female fetus were compared to women with a male fetus with respect to their rate of asthma exacerbation, their weekly doses of inhaled short-acting beta(2)-agonists (SABA), and their daily dose of inhaled corticosteroids (ICS) during pregnancy. Logistic and linear regression models were used to obtain effect measures adjusted for several potential confounders such as asthma severity and control prior to pregnancy. The cohort included 5529 pregnancies with a single female fetus and 5728 pregnancies with a single male fetus. No significant differences were found between mothers of a female and male fetus as to the occurrence of asthma exacerbations (adjusted rate ratio=1.02; 95% CI: 0.92-1.14), the daily dose of ICS (adjusted mean difference (AMD): 2.46 microg; 95% CI: -4.01 to 8.93), and the weekly dose of SABA (AMD: 0.004 dose; 95% CI: -0.23 to 0.24). Based on the results, we conclude that fetal gender is unlikely to affect maternal asthma during pregnancy to the point where acute care and medications are more often required among women pregnant with a female fetus.

Because of residual confounding by asthma severity, our study was not able to show that women who stopped inhaled corticosteroids during pregnancy were at increased risk of having an asthma exacerbation. However, women who stopped corticosteroids tended to have a milder form of asthma, which is reassuring and suggests that women can recognize, to a certain extent, the need to continue taking their controller agents if necessary.