Effects of smoking cessation on maternal airway function and birth weight

Objective: To evaluate the effects of smoking cessation before or early in pregnancy on maternal airway function and birth weight. Methods: Measurements of forced expiratory spirometry including forced vital capacity, forced expiratory volume in 1 second, forced expiratory flow rates between 0.2 and 1.2 L, 25% and 75%, and 75% and 85%, and instantaneous flows at lung volumes of 25%, 50%, and 75% were carried out by a wedge bellow spirometer in 40 pregnant exsmokers and were compared with those of 175 nonsmoking and 97 currently smoking pregnant women. Spirometric testing was conducted at a mean (± SD) gestational age of 21.5 ± 7.0 weeks. In exsmokers, the average lifetime cigarette consumption was 17.1 ± 8.1/day for a mean duration of 9.7 ± 3.9 years, similar to that observed in current smokers. The median duration of smoking abstinence was 20 weeks before study spirometry. Results: All spirometric measurements in exsmokers were similar to those of nonsmokers and were significantly higher than those of current smokers. Spirometric measurements for nonsmokers, current smokers, and exsmokers were respectively: forced expiratory volume in 1 second (3.36 ± 0.39, 3.09 ± 0.45, and 3.35 ± 0.32 L); forced expiratory flow rate between 25% and 75% (ie, mid–expiratory phase) (3.85 ± 0.69, 3.21 ± 0.76, and 3.86 ± 0.66 L/sec); forced expiratory flow rate between 75% and 85% (ie end–expiratory phase) (1.39 ± 0.35, 1.03 ± 0.35, and 1.41 ± 0.39 L/sec); instantaneous flow at lung volume of 50% (4.35 ± 0.82, 3.76 ± 0.89 and 4.36 ± 0.68 L/sec); and instantaneous flow at lung volume of 25% (1.91 ± 0.47, 1.47 ± 0.49, and 1.92 ± 0.46 L/sec). Mean gestational age at delivery was similar among the three groups (277 ± 11, 274 ± 12, and 274 ± 11 days for nonsmokers, current smokers, and exsmokers, respectively). The mean birth weight of babies born to exsmokers (3408 ± 511 g) was similar to that of babies born to nonsmokers (3469 ± 461 g), but was significantly greater than that of babies born to smoking pregnant women (3189 ± 485 g; P < .001). Conclusion: Smoking cessation either before or at an early stage of pregnancy is associated with early, reversible increments of maternal airway function and mean birth weights that are higher than among women who continue smoking.