Between 1998 and 2006, mothers of 5,323 non-malformed infants in Massachusetts were located and approached for participation; 3,609 (67.8%) agreed to be interviewed. Overall, 502 women (13.9%) met our definition of provider-diagnosed asthma; an additional 578 (16.0%) were classified as possible asthma and 137 (3.8%) as past asthma ().
Rates of Asthma Among 3609 Mothers of Normal Newborns
Physician-diagnosed asthma was most prevalent among the youngest women, and decreased with age (). Higher prevalences were also observed among women who were white, obese, had less than high school education, smoked during pregnancy, and lived in households with 5 or more members. Similarly, possible asthma was more prevalent among women who were young, less well-educated, and who smoked during pregnancy, but, in contrast to physician-diagnosed asthma, possible asthma was most common among underweight women (BMI less that 18.5), and was not associated with household size. Restricting subjects to those with physician-diagnosed asthma (), women classified as poorly-controlled tended to be older, less well-educated, smoke during pregnancy, have lower family incomes, and live in larger households than women with well-controlled asthma, although only the relationships with lower income and larger household size were statistically significant. Women in the not well-controlled category were more likely to be over age 24 and in the lowest income group.
Prevalence of Asthma According to Selected Factors Among 3609 Mothers of Normal Newborns*
Asthma Symptom Control According to Selected Factors Among 502 Mothers with Provider-diagnosed Asthma
There was no significant trend over time in the prevalence of physician-diagnosed asthma, but the proportion of women with possible asthma declined from 21% to 10% (p<.05) between 1997 and 2005 (data not shown).
The relationship between pregnancy and asthma symptoms varied considerably according to degree of symptom control (). While, overall, about half (53%) of women with provider-diagnosed asthma reported no change in symptoms, the proportion varied from 41% among poorly-controlled to 69% among well-controlled subjects. Those whose symptoms changed were almost equally divided between those who improved (24.6%) and those who worsened (22.4%). Women with poorly-controlled asthma were more likely to report improvement (34.9%) than women with not well-controlled (23%) or well-controlled asthma (16.7%). Worsening of symptoms was almost equally likely to occur in any trimester (6.7%-7.9%), whereas improvement was noted somewhat more often in the first trimester (11.8% vs. 8.3% or 4.5%).
Changes in Asthma Symptoms during Pregnancy.
To consider rates of asthma medication use according to asthma status, we examined drugs reported by study subjects to have been used for asthma (indication-based medication use); to capture use among women who had undiagnosed or unknown asthma (and therefore would not report medications use “for asthma”), we also examined drugs known to be used in the treatment of asthma (class-based medication use) (). For both drug groups, rates were highest among those with provider-diagnosed asthma and within that category use declined with better symptom control; there was very little use among subjects with possible or past asthma. Of note, 63.3% of women whose asthma symptoms were poorly controlled did not use a controller medication during pregnancy. As expected, among women classified as non-asthmatics, none reported using a medication to treat asthma, although 4.1% reported use of a recognized asthma medication for other indications, such as colds or allergy.
Use of Asthma Drugs Among 3609 Mothers of Normal Newborns According to Asthma Status.
To explore possible trends in the use of asthma medications over time, we restricted our analyses to women with provider-diagnosed asthma and investigated use according to year of LMP. Among the drug classes, there were no significant trends in use of any asthma drug, any steroid, any beta-2 agonist, or any other asthma medication (), nor did use of steroids by specific route change significantly (). Virtually all beta-2 agonist use was via inhalation.
Trends in the Use of Asthma Medications During Pregnancy Among 502 Mothers with Provider-Diagnosed Asthma.
Trends in the Use of Corticosteroids During Pregnancy Among 502 Mothers with Provider-Diagnosed Asthma.
According to lunar month of pregnancy, rates of use of inhaled steroids and beta-2 agonists were nearly constant for the period beginning 2 months prior to the LMP through the 4th lunar month. Inhaled steroids declined from 5% before pregnancy to 4.5%, and for beta-2 agonists the corresponding rates were 16% and 14% (data not shown).
Use of other asthma medications, including leukotriene modifiers and combination products (e.g., Advair®), was generally low, but use of leukotriene modifiers increased consistently over time, and use of combination products increased significantly (p<.01), consistent with their recent introduction to the market ().
Trends in the Use of Selected Asthma Medications Among 502 Mothers with Provider-Diagnosed Asthma.
The most commonly reported specific asthma medications were albuterol (53%), fluticasone (9.4%), beclomethasone (5.2%), and budesonide (3.0%). Over the study years, only use of fluticasone changed significantly, from 2.4% to 8.4% (p<.05), perhaps due to its relatively recent introduction in 1997 (data not shown).