Izci-Balserak B, et al. - This was a secondary analysis of a prospective study which intended to illustrate changes in sleep as measured by polysomnography (PSG) and spectral electroencephalogram (EEG) bands during pregnancy, as well as explored the association between delta power in non-rapid eye movement (NREM) sleep and sleep-disordered breathing (SDB). For this analysis, 123 women had full PSG in early pregnancy, and 97 repeated PSG in late pregnancy. The results of this study revealed that PSG-measured sleep characteristics change during pregnancy. It was observed that delta power decreases when the severity of SDB increases during pregnancy.