Periodic sleep apnea, a chronic sleep deprivation state, in which marked changes in the arterial PO2 and PCO2 tensions have been recorded, is a relatively new syndrome not previously reported in pregnancy. It is characterized by episodes of apnea, prevalently obstructive, during sleep. The majority of patients with this syndrome have snored heavily for years, suggesting a causal relationship between snoring and periodic sleep apnea. The effects of prolonged snoring on alveolar ventilation and systemic pressure(s) suggest that this snoring has physiopathological implications on maternal cardio-respiratory reserve and indirectly upon the fetus, especially as there are recordable changes in fetal heart rate and also a change in the acid-base status of the fetus. The possibility that this syndrome may have an adverse effect upon the fetus is stressed.