Current treatment guidelines emphasise the importance of use of several asthma medications during pregnancy, as uncontrolled asthma has been associated with an increased risk of low birth weight (LBW), preterm birth (PB) and small for gestational age (SGA).
There are however limited data on the safety of long-acting β2-agonists (LABAs) during pregnancy. In addition, although several studies have failed to find any statistically significant association between use of inhaled corticosteroids (ICSs) during pregnancy and risk of LBW, PB and SGA, some of the relative risks reported have been high (suggesting an undetected risk, with the studies possibly having an insufficient power), and the effects of different doses have only rarely been considered.
The purpose of the current research was to further investigate the safety of use of LABAs and different doses of ICSs during pregnancy on LBW (<2500 g), PB (delivery before 37 weeks’ gestation) and SGA (birth weight below the 10th percentile). The cohort comprised 7,376 pregnancies from 6,199 women with asthma between 2002 and 2008 in Quebec, Canada, identified from administrative databases. The main overall findings were that LABA use was not associated with increased prevalence of LBW, PB or SGA, but that there was a non-significant trend towards an increased prevalence of the three outcomes with increasing doses of ICS above 125mcg/day (fluticasone propionate equivalent).
The authors note that the use of higher doses of ICS could be seen as a marker of more severe and/or difficult-to-control asthma, which may confound the association between ICS use and perinatal outcomes. Other limitations highlighted include a possible underestimation of the effects of LABA (some women received only a month’s supply during pregnancy), the imprecision when calculating ICS exposure (especially the low-dose category, which included varying patterns of use, such as a single short course of high-dose ICS), and the fact that some risk factors could not be controlled for (e.g. poor maternal nutrition, obesity, alcohol intake).
The authors comment that additional study is required to better evaluate the safety of higher-dose ICS during pregnancy, but they conclude that the currently available data suggests use of LABA and higher-dose ICS to maintain asthma control during pregnancy would outweigh their potential risks.