Sleep is a complex but essential biologic process and a time for essential housekeeping functions to occur in the brain. Normal human sleep is composed of rapid eye movement (REM) sleep and stages N1, N2, and N3 of non-REM (NREM) sleep. The body of living things has circadian clocks and its fundamental function is to synchronize energy harvesting and utilizing process with the rising and the setting of the sun. Hormones such as melatonin play an important role in circadian regulation. The different kinds of sleep disturbances associated with metabolic syndrome and diabetes are insufficient sleep, excessive sleep, fragmented sleep, circadian disruption and circadian misalignment. The obstructive sleep apnea (OSA) is a complex disorder associated with reductions in sleep duration, quality and intermittent hypoxia (IH). Physical and hormonal changes affect sleep in pregnancy and several studies report that sleep disordered breathing (SDB) during pregnancy was associated with gestational diabetes mellitus The treatment with continuous positive airway pressure (CPAP) improves these outcomes.