Severe obstructive sleep apnea, a disturbance of sleep resulting from intermittent periodic obstruction of the upper airway, was diagnosed after cardiotocography during which the external tocodynamometer disclosed a pattern initially thought to represent uterine activity. In spite of this obstructive sleep apnea with associated markedly low, hypoxic oxygen saturation levels and daytime somnolence of 10 to 12 hours from 32 weeks until delivery, subsequent fetal outcome was good.