Objective: To evaluate the differences in sleep of women throughout pregnancy compared with those of nonpregnant control subjects.
Study design: Four pregnant women were studied longitudinally during their pregnancy using inpatient polysomnography. Measurements included electroencephalography, electrocardiography, and continuous-pulse oximetry. Four healthy nonpregnant women matched for age and weight were used as control subjects. The total sleep time was recorded, and percentages of each sleep stage were generated.
Results: Qualitative differences in sleep between pregnancy patients and control subjects were evident. Control subjects displayed a normal appearance of slow-wave sleep in stages 3 and 4 (delta sleep). When pregnant patients did display delta sleep, it appeared abnormal secondary to extensive alpha-wave intrusion. Even when including this abnormal delta sleep in a quantitative comparison, the pregnant patients had a significantly shorter percentage of total sleep time in delta sleep (4.9+/-1.9% vs 21.9+/-6.0%, p=0.03).
Conclusion: Sleep in pregnancy is characterized by loss of normal slow-wave sleep. Thus, sleep stages 3 and 4 are shortened during pregnancy. This sleep alteration is persistent when followed longitudinally during pregnancy.