Fetal breathing: a clinically useful paradox

Abstract

Purpose: To examine fetal breathing movements in fetuses with congenital diaphragmatic hernia and compare this to unaffected fetuses and with their outcome after birth.Methods: Twenty women with normal singleton pregnancies and four cases of congenital diaphragmatic hernia were studied. All fetuses were observed for 60 min at 36 weeks of gestation. Fetal breathing movements were observed by scan taking a cross‐sectional view across the abdomen. The scan was recorded and breathing movements analyzed off‐line. All sessions occurred at the same time of the day and two hours after a light meal. No patients were cigarette smokers. Bouts of fetal breathing activity were defined as the length in seconds of each series of successive individual breathing movements bracketed by periods of apnea. The absence of fetal breathing movements for more than 3 s was called the apnea period. Total duration of breathing was the sum of all bouts.Results: The normal fetuses exhibited a breath to breath interval of 1.3 s and displayed breathing movements for around 30–35% of the observation period. Of the four fetuses with congenital diaphragmatic hernia, three died during the neonatal period due to lung hypoplasia, one survived following surgical repair. All four fetuses exhibited a similar breath to breath interval as unaffected fetuses but the three fetuses who died spent 80% (range 70–90%) of the time breathing whereas the fetus that survived spent 32% of its time breathing. Increased yawning was also observed in the fetuses who died.Conclusions: It has been speculated that the inhibition of fetal breathing movements may result in pulmonary hypoplasia, yet fetuses with lung hypoplasia spend more time breathing than those without lung hypoplasia. The relationship between breathing movements and lung development requires further study. Breathing movements may provide important information on fetal health and outcome.