The Effect of ร 2 -agonists and Inhaled Corticosteroids Used to Treat Asthma in Pregnancy on Fetal Growth.
While inadequate control of asthma during pregnancy has been associated with adverse pregnancy outcomes, the effect of inhaled corticosteroids (ICS) and ร 2agonists on fetal growth is uncertain. In this prospective study we describe the effect of these medications on fetal growth among 679 asthmatic pregnant women (173 used ร 2 -agonists only and 506 used ICS with or without other medications) and 310 controls recruited in 1998-2003 through the Organization of Teratology Information Services. More women in the ร 2agonist group had BMI >28 (30.1%) compared to women in the ICS group (24.7%) and controls (13.6%); no differences in asthma severity were observed among asthmatics. Women in the ร 2 -agonist group had a significantly lower proportion of infants 10 th percentile on birth weight (1.7%) compared to the ICS group (7.1%) and controls (5.2%) (p=0.027). After adjustment for asthma severity, gravidity, parity, ethnicity, smoking, alcohol use, maternal age, and pre-pregnancy BMI, ร 2 -agonists remained protective for birth weight 10 th percentile relative to the ICS (OR=0.24; 95% CI 0.07; 0.79). When treatment groups were compared to controls, direction of effect remained the same but was not statistically significant (ร 2 -agonists: OR=0.36; 95% CI 0.10; 1.29; ICS: OR=1.70; 95% CI 0.91; 3.17). Use of ร 2 -agonists in pregnancy is associated with a lower incidence of small for gestational age infants relative to infants prenatally exposed to ICS or born to non-asthmatic controls. The effect could be attributed to induced relative carbohydrate intolerance, altered uteroplacental hemodynamics, or inhibition of the growth hormone axis.