During the past fifteen years the obstructive sleep apnea syndrome (OSAS) has become widely recognized as a quite common disorder with a wide range of serious clinical complications (1, 2, 3). This syndrome arises as a result of sleep related changes in upper airway muscle function and progressive narrowing of the oropharyngeal lumen. The resulting hypoxia (or asphyxia) leads to an arousal response that terminates the initial obstructive event. The exact incidence and prevalence of OSAS is currently unknown. Lavie (4) concluded its prevalence to be 1.26 percent. Others (5, 6) found that the prevalence of heavy regular snoring (taken as an index of at least a partially obstructed airway) increased with age including 40 percent of women and 50 percent of men over 60 years of age. Polygraphically documented OSAS showed incidence of 0.99 percent in an unselected population. Postmenopausal women have frequent episodes. of OSA in contrast with their premenopausal counterparts, who very rarely have any apnea. Since we could not find in the literature any documented OSAS studies in pregnancy, we would like to base our hypothesis on our previously published clinical observations and our recent findings. In the present paper we would like to suggest that pathophysiologic changes of OSAS prolonged throughout many weeks of pregnancy may have an adverse effect upon the feto-placental unit.