Obstructive sleep apnea during pregnancy, associated with arterial hypertension, pre-eclampsia and adverse outcome of the newborn, has been described. Usually it can successfully be treated with non-invasive ventilation. A 36-year-old, twin-pregnant woman at 28 + 6 weeks of gestation presented with the complaints of snoring and nocturnal oxygen desaturations. Polysomnography confirmed the diagnosis of severe obstructive sleep apnea (respiratory disturbance index [RDI] 104/h, minimal oxygen saturation in pulse oximetry [SpO2/min] 75%). First therapeutic approaches including oxygen supplementation, non-invasive ventilation with continuous positive airway pressure (CPAP) or bilevel positive airway pressure--spontaneous (BiPAP-S) remained without success. Only after ventilation with bilevel positive airway pressure in spontaneous/timed modus (BiPAP-ST) combined with additional oxygen supplementation a satisfactory treatment result could be achieved (RDI 32/h, SpO2/min 85%). Because of progressive pre-eclampsia despite therapy at 31 + 0 weeks of gestation cesarean section was performed and 2 healthy children were delivered. After surgery non-invasive ventilation had to be continued for another six weeks before the condition improved. In contrast to the documented benefits of non-invasive positive pressure ventilation in pregnant women the literature, in our case even with sufficient therapy of sleep apnea progressive pre-eclampsia and premature delivery could not be prevented. Possible explanations include the short treatment duration and existence of twin pregnancy.