Abstract

Thoracic gas volume (TGV), resting lung volume at end expiration, was measured by the plethysmographic technique in 9 infants with Werdnig-Hoffmann disease. Five of these infants were considered to have intrauterine onset of the disease; the mother in each case had reported a pronounced reduction in fetal activity during the last trimester of pregnancy, and 4 were found to be hypotonic at birth. The remaining 4 infants appeared normal at birth and did not develop any signs of the disease until between 2 and 12 weeks postnatally. Those with intrauterine onset of disease had a significantly reduced TGV (mean 20.8 ml kg(-1)), whereas those with postnatal onset had normal lung volumes (means 36.1 ml kg(-1)). The reduction in lung volume correlated only with intrauterine onset of disease, and was not related to either the degree of muscle weakness or the duration of disease. There is increasing evidence that fetal breathing movements may be one of the essential prerequisites for normal fetal lung development. It is therefore possible that diminished fetal breathing movements, resulting from weakness of the respiratory musculature in utero, could be responsible for the reduction in lung volume found in those infants with intrauterine onset of the disease.