Increased platelet volume and aggregation precede the onset of preeclampsia.

OBJECTIVE: To determine whether changes in platelet aggregation, numbers, or mean volume precede the onset of preeclampsia in patients given anti-platelet therapy.
METHODS: Changes in platelet aggregation, numbers, and volumes were followed longitudinally in 17 women who had previously lost 44 of 56 pregnancies and were thus considered to be at risk of preeclampsia. The subjects were treated with low-dose aspirin. Mean platelet volume, platelet numbers, and platelet aggregation were monitored every 2-4 weeks during pregnancy.
RESULTS: All eight subjects who developed preeclampsia delivered growth-retarded infants before term. All showed increased platelet aggregation in vitro, accompanied by increased platelet volumes (by at least 0.8 fL) and decreased platelet numbers (by at least 60 x 10(9)/L) in five subjects, increased volumes alone in one, and decreased numbers alone in one. The increases in platelet aggregation and volumes predated the development of preeclampsia by 2-5 weeks. Nine subjects had pregnancies that progressed normally to term (beyond 37 weeks), with the delivery of eight normal and one growth-retarded infant; platelet aggregation, numbers, and volumes did not change to the same extent as in the subjects who developed preeclampsia.
CONCLUSION: Increased mean platelet volume and increased platelet aggregation compared to the individual patient's first-trimester data were detected 2-5 weeks before the development of all cases of preeclampsia. In contrast, normal pregnancies did not show significant changes in mean platelet volume or platelet aggregation.