Maternal middle cerebral artery velocimetry in normal pregnancy and postpartum

Objective To study changes throughout gestation and the puerperium of middle cerebral artery flow velocity waveforms obtained by transcranial Doppler ultrasound. Design Prospective, observational study. Setting John Radcliffe Maternity Hospital, Oxford, UK. Participants and Methods Middle cerebral artery velocities were measured by transcranial Doppler ultrasound in 25 nonpregnant women, 22 women longitudinally followed throughout pregnancy and 21 women serially studied from delivery until the late puerperium. Main outcome measures Transcranial Doppler changes in pregnancy and the puerperium. Results The transcranial Doppler ultrasound measurements showed good reproducibility. Signals from one middle cerebral artery could not be obtained in 4.6% of the examinations, but otherwise readings were similar on both sides. Women in the second half of pregnancy had lower middle cerebral artery mean velocities than nonpregnant women. Velocities decreased with advancing gestation but increased in the immediate puerperium to levels comparable to those found in nonpregnant women. Conclusions Transcranial Doppler ultrasound is a noninvasive technique suitable for studying maternal cerebral haemodynamics in pregnancy and postpartum. Middle cerebral artery mean velocity decreased with advancing gestation and increased to nonpregnant values in the immediate puerperium. These physiological changes need to be considered when comparing data with measurements taken in abnormal pregnancy states.