Lee was able to study a group of women before they were pregnant, during their pregnancy and for three months postpartum. During their first trimester, she found an increase in total sleep time but poorer quality sleep due to awakening during the night. She also found a decrease in deep sleep from pre-pregnancy to the first trimester. The women didn't say, 'I had 10% less delta sleep last night,' but they did complain of feeling fatigued, drowsy, and even depressed.