Do maternal cerebral vascular changes assessed by transcranial Doppler antedate pre-eclampsia?

To determine whether maternal transcranial Doppler (TCD) evaluation of the middle cerebral artery identifies changes in the cerebral circulation prior to the development of pre-eclampsia.

In a nested, case-controlled study developed from a previous prospective cohort study, 20 pre-eclamptic and 40 normotensive pregnancies, matched for maternal age, were assessed with the traditional middle cerebrovascular Doppler parameters (pulsatility index, mean cerebral blood flow velocity), together with non-traditional Doppler parameters including time taken to achieve end systole (EST) and percentage time to achieve end systole (% EST). Assessments done at 20-24 and 28-32 weeks' gestational age were compared using Student's t-tests. Significance was set at the P < 0.05 level.

In the second trimester (20-24 weeks) there were no significant differences in any of the Doppler waveform characteristics in either group. In the third trimester (28-32 weeks) there was a significant increase in the % EST in the group who subsequently developed pre-eclampsia (45.2 +/- 4.2 vs. 42.3 +/- 4.1; P < 0.01).

Patients who subsequently develop pre-eclampsia show a significant lengthening in the EST in the third trimester as a late finding, which indicates an increase in the cerebrovascular resistance. Earlier prediction of pre-eclampsia using TCD waveform analysis will require more provocative testing (i.e. hand grip and CO(2) reactivity).