Changes in exhaled breath condensate pH in healthy and asthmatic pregnant women

Objective: Asthma is a common chronic disease complicating pregnancy with a risk for perinatal complications. Control of airway inflammation in the asthmatic pregnancy improves pregnancy outcomes. Our aim was to evaluate pH of exhaled breath condensate (EBC), a non-invasive method for the assessment of asthmatic airway inflammation, in healthy and asthmatic pregnancies.

Design: Cross-sectional study.

Setting: Hungarian university clinics.

Population: Seventeen healthy pregnant women, 21 asthmatic pregnant women, 23 healthy non-pregnant women and 22 asthmatic non-pregnant women.

Methods: EBC samples were collected using a portable condenser, EBC pH was measured after argon deaeration.

Main outcome measure: EBC pH.

Results: EBC pH (mean ± SD) of healthy non-pregnant and asthmatic non-pregnant women was similar (7.75 ± 0.27 vs. 7.54 ± 0.57; p = 0.118), probably indicating an optimal control of airway inflammation in asthmatic women. On the other hand, EBC pH was higher in healthy pregnant women compared with healthy non-pregnant women (8.02 ± 0.43 vs. 7.75 ± 0.27; p = 0.017). Higher EBC pH accompanying healthy pregnancy was absent in asthmatic pregnant patients whose EBC pH was lower (7.65 ± 0.38) than that of healthy pregnant women (p = 0.006), and it was similar to that in asthmatic and healthy non-pregnant women (p = 0.470 and p = 0.300, respectively). The EBC pH in asthmatic pregnant women correlated positively with birthweight (r = 0.49, p = 0.047) and negatively with forced vital capacity (r = 0.45, p = 0.039). EBC pH was not related to blood pH.

Conclusions: EBC pH is higher in healthy pregnant women but not in asthmatic pregnant women compared with data from healthy non-pregnant women, indicating that oxidative inflammatory processes induced by asthma may compromise the regulatory mechanisms causing alkaline pH in the airways during pregnancy.