Morten M, et al. - In Managing Asthma in Pregnancy (MAP) trial in Newcastle, Australia, 50% reduction in asthma exacerbations during pregnancy was noted subsequent to employment of a treatment algorithm using the fraction of exhaled nitric oxide (FeNO) in combination with asthma symptoms (FeNO group) in pregnant asthmatic women, compared with a treatment algorithm using clinical symptoms only (clinical group). Herein, the effect of FeNO-guided asthma management during pregnancy on asthma incidence in childhood was determined. It was noted that FeNO-guided asthma management during pregnancy prevented doctor diagnosed asthma in the offspring at preschool age. This effect was in part mediated via changes in use and dosing of inhaled corticosteroids during the MAP trial.

• The effect of FeNO-guided asthma management on childhood asthma incidence was determined in the Growing Into Asthma (GIA) double-blind follow-up study after receiving consent from a total of 179 mothers.

• Follow-up was carried out in 140 children (78%) at 4 to 6 years of age.
• A significant reduction in doctor diagnosed asthma was noted as a result of using FeNO-guided as compared to symptoms only based approach (25·9% vs 43·2%; odds ratio [OR] 0.46, 95% confidence interval [CI] 0.22 to 0.96, p=0.04).
• Furthermore, in children born to mothers from the FeNO group, the following were less commonly seen: frequent wheeze (OR 0.27; CI 0.09 to 0.87, p=0.03), use of short-acting beta agonists (OR 0.49; CI 0.25 to 0.97; p=0.04), and Emergency Department visits for asthma (OR 0.17, CI 0.04 to 0.76; p=0.02) in the past 12 months.
• Findings demonstrated that doctor diagnosed asthma was related to common risk alleles for early-onset asthma at gene locus 17q21 (p=0·01 for rs8069176; p=0·03 for rs8076131), and higher airways resistance (p=0·02) and FeNO levels (p=0·03).
• In addition, a causal mediation analysis suggested natural indirect effects of FeNO-guided asthma management on childhood asthma through "any use" and "time to first change in dose" of inhaled corticosteroids during the MAP trial (OR 0.83; CI 0.59 to 0.99 and OR 0.90, CI 0.70 to 1.03, respectively).