A 26 yr old puerperal female with Hallermann-Streiff syndrome developed serious obstructive sleep apnoea syndrome during pregnancy. She underwent an elective Caesarean section delivery, but ending the pregnancy did not improve her clinical symptoms. By treating her with nasal continuous positive airway pressure, a worsening of her headaches and glaucoma was prevented. The administration of acetazolamide controlled all of her symptoms. Treatment with nasal ventilation is the best initial approach. It is also important to assure normal oxygenation before pregnancy since the foetus may suffer from the severe deprivation that may occur in these patients.