Severity of asthma in pregnancy affects perinatal outcomes: Authors' Reply

We read with great interest the recent review on adverse perinatal outcomes in women with asthma by Murphy et al. Maternal asthma is a potentially dangerous reversible anoxigenic condition, which adversely affects perinatal outcomes. The most important factor affecting perinatal outcome is the severity and control of asthma. Earlier studies reported that prematurity, low birthweight, fetal growth restriction and even perinatal deaths were more frequent in pregnant women with asthma. In our experience, mild asthma during pregnancy had no significant effect on fetal growth, as evidenced by a normal mean birthweight. In contrast, severe maternal asthma requiring repeated hospital admission is associated with a 373 g reduction of mean birthweight compared with healthy controls (2842 versus 2469 g; P < 0.05), although the mean gestation at birth in both groups was approximately 38 weeks. In the mild asthma group, such growth restriction was conspicuously absent. Furthermore, severe asthma was associated with a significantly higher incidence of low-birthweight infants compared with healthy controls and compared with births to women with mild asthma (P < 0.01). Although Murphy et al. found a moderate reduction of birthweight (93 g) in the infants of asthmatic mothers, no attempt was made to correlate this with the severity of the asthma or its acute exacerbations.1 The extent of maternal–perinatal hypoxia in asthma is likely to be related to the severity, frequency and duration of the hypoxic spells. Therefore, the general statement that ‘pregnant women with asthma are at significantly increased risk of a range of adverse perinatal outcomes…’ is probably an oversimplification of the problem.1