The effect of cigarette smoking on asthma control during exacerbations in pregnant women Vanessa E Murphy, 1 Vicki L Clifton, 2 Peter G Gibson 3 ABSTRACT Background Smoking and severe asthma exacerbations in pregnancy are risk factors for low birth weight babies. No studies have assessed the clinical implications of smoking on asthma exacerbations in pregnancy. Methods Pregnant women with current asthma (n¼80) were prospectively assessed at clinic visits (18, 30, 36 weeks), during exacerbations and with fortnightly phone calls. The asthma control questionnaire was administered at each contact and exacerbations classified as severe (requiring medical intervention) or mild (self-managed). Medications, self-management skills, smoking history, fractional exhaled nitric oxide (FENO), exhaled carbon monoxide (ECO) and lung function were assessed. Pregnant women without asthma (controls, n¼46) were assessed prospectively at clinic visits. Results Women with asthma were more likely to smoke (34% current smokers) than women without asthma (15% current smokers). In women with asthma, the median (IQR) exacerbation rate during pregnancy was 2.0 (1.0e3.0) in current smokers, 2.0 (1.0e3.0) in ex-smokers and 1.5 (1.0e2.0) in never smokers. The asthma control score during exacerbations was higher in current smokers (median (IQR) 2.17 (1.17e2.7)) compared with never smokers (1.17 (0.8e2.17), p¼0.056). An adjusted linear regression model found that smoking was significantly associated with higher asthma control score during exacerbation (p¼0.04). Birth weights were lower among children of smokers than non-smokers (p¼0.023 control group, p¼0.086 asthma group). Conclusions During pregnancy, asthma exacerbations are more common and more severe in current smokers than never smokers. The risk of effects of maternal asthma on the fetus may be greater among smokers. INTRODUCTION Smoking during pregnancy is a significant risk factor for poor perinatal outcomes, including low birth weight, premature birth and infant mortality. 1 Despite this, many pregnant women continue to smoke during pregnancy. In Australia, the rate of smoking among pregnant women is w20%, and the quit rate in pregnancy is surpris- ingly low, with heavy smokers less likely to quit. 2 Studies from around the world have suggested that pregnant women with asthma are more likely to smoke than pregnant women without asthma, 3e14 with few exceptions. 15e17 Women with asthma are also at an increased risk of low birth weight, 18 and severe asthma exacerbations during pregnancy are associated with a 2.5-fold increased risk of low birth weight. 19 Thus, women with asthma who smoke during pregnancy may be at increased risk of low birth weight from the combined effects of smoking, asthma and severe asthma exacerbations. There is also the potential for smoking to worsen asthma control during pregnancy, and further increase risks to the fetus. Smoking is associated with persistent changes in asthma, including a greater decline of lung function with age, 20 poorer symptom control 21 and reduced response to corticosteroids. 22 It was previously found that asthma control among non-pregnant adult smokers was worse than in non-smokers 21 and that smokers had significantly higher scores for each individual item than never smokers, with the exception of lung function. 21 There are limited studies investigating the frequency or severity of exacerbations among smokers with asthma compared with non-smokers with asthma, with some evidence that current smokers report more frequent symptoms, 23 and may have a higher risk for hospitalisation for acute asthma. 24 Asthma control and exacerbations have not previously been assessed in smokers during preg- nancy. We hypothesised that pregnant women with asthma who were current smokers would experience more frequent exacerbations than never smokers, and that these exacerbations would be more severe, indicated by a higher asthma control questionnaire (ACQ) score. METHODS Pregnant women (18e43 years) were consecutively recruited through the John Hunter Hospital ante- natal clinics and the community between July 2004 and December 2006. Women signed written informed consent for participation. Approval was provided by the University of Newcastle and Hunter New England Health Human Research Ethics Committees. A research midwife located in the antenatal clinic explained the study to poten- tially eligible participants, and referred those potentially interested to research staff who obtained written informed consent. This approach allowed prospective recruitment of consecutive new referrals to the antenatal clinic. Pregnant women with physician-diagnosed asthma (n¼85) were prospectively followed from recruitment (mean 14.8, SD (3.0) weeks gestational age) with clinic visits at w18, 30 and 36 weeks gestation (visit 1, 2 and 3), and fortnightly phone calls between visits. Women were assessed during exacerbation where possible. Four women with asthma did not have current symptoms or medi- cation use during the pregnancy and were consid- ered in remission. One woman completed one visit and insufficient data about smoking status were available. Results from these five women were excluded from the present analysis. The ACQ6 25 was administered at each contact. The ACQ is a validated tool assessing the severity < Supplementary material is published online. To view these files please visit the journal online (http://thorax.bmj.com). 1 Centre for Asthma and Respiratory Diseases, University of Newcastle and Hunter Medical Research Institute, Australia 2 Department of Paediatrics and Reproductive Health, University of Adelaide, Australia 3 John Hunter Hospital, Australia Correspondence to Dr Peter G Gibson, Department of Respiratory and Sleep Medicine, Level 3, John Hunter Hospital, Locked Bag 1, HRMC, Newcastle NSW 2310, Australia; peter.gibson@ hnehealth.nsw.gov.au Received 5 August 2009 Accepted 18 April 2010 Thorax 2010;65:739e744. doi:10.1136/thx.2009.124941 739 Smoking on June 15, 2020 by guest. Protected by copyright. http://thorax.bmj.com/ Thorax: first published as 10.1136/thx.2009.124941 on 13 July 2010. Downloaded from