Fetal breathing during chronic lung liquid loss leading to pulmonary hypoplasia

The mechanism of oligohydramnios-related pulmonary hypoplasia (PH) is not understood, but is known to involve chronic loss of lung liquid. In order to investigate the recent suggestion that fetal breathing movements are absent or diminished in oligohydramnios-related PH, we made continuous recordings of fetal breathing movements (FBM) during chronic lung drainage in tracheostomized fetal sheep. FBM remained present throughout the drainage period. There was no significant difference in the number or duration of FBM epochs in tracheostomized fetuses compared to controls, although there was a slight reduction in incidence between 126 and 133 days (P = 0.02). PH in the fetuses undergoing chronic lung liquid drainage was confirmed by significant reductions in lung weight, volume, DNA, and total airspace, and in altered maturation. This study is consistent with other data suggesting that inhibition of FBM is not the primary mechanism of oligohydramnios-related pulmonary hypoplasia.