Anatomical, physiological, psychological and hormonal alterations affect sleep during pregnancy. Sleep appears tobe commonly impaired only after the first trimester. Albeit objective data regarding the reduction of sleep durationand efficiency are not univocal, poor sleep is reported by over half of pregnant women. The reasons underlyingthese complaints are multiple, including lower back pain, gastroesophageal reflux disorder (GERD), increasedmicturition and repositioning difficulties at night. Specific primary sleep disorders whose prevalence drasticallyincreases during pregnancy include obstructive sleep apnea (OSA) and restless legs syndrome (RLS), both relatedto gestational hypertension and gestational diabetes mellitus (GDM). Pre-eclampsia and labor complicationsleading to an increased number of cesarean sections and preterm births correlate with insomnia and OSA inparticular. Post-partum depression (PPD) and impairment of the mother-infant relationship may also be consideredas secondary effects deriving from poor sleep during pregnancy. Recognition and treatment of sleep disordersshould be encouraged in order to protect maternal and fetal health and prevent dire consequences at birth.