New mothers often complain of impaired cognitive functioning, and it is well documented that women experience a significant increase in sleep disturbance after the birth of a child. Sleep disturbance has been linked to impaired cognitive performance in several populations, including commercial truck drivers, airline pilots, and medical residents, though this relationship has rarely been studied in postpartum women. In the present study 13 pregnant women and a group of 22 non-pregnant controls completed one week of actigraphy followed by a battery of neuropsychological tests and questionnaires in the last month of pregnancy (Time 1) and again at four weeks postpartum (Time 2). Pregnant women experienced significantly more objective and subjective sleep disturbance than the control group at both time points. They also demonstrated more impairment in objective, but not subjective cognitive functioning. Preliminary analyses indicated increased objective sleep fragmentation from Time 1 to Time 2 predicted decreased objective cognitive performance from Time 1 to Time 2, though small sample size limited the power of these findings. Implications for perinatal women and need for future research were discussed.