Retrospective analysis of platelet numbers and volumes in normal pregnancy and in pre-eclampsia

To determine the distribution of platelet volumes and numbers through pregnancy, and to compare these to changes in platelet volumes and numbers in women with pre-eclampsia.

Four hundred twenty-eight women with normal pregnancy from whom four or more platelet measurements were available were identified. 74 women with pre-eclampsia (blood pressure > or = 140/90 mmHg, at least 0.5 g protein/24 h urine collection) from whom platelet measurements were available between 27 and 30 weeks of gestation were identified.

Mean platelet volume and platelet number remained constant in normal pregnancies between the first trimester and the end of pregnancy. A persistent increase of > or = 0.8 fl (> or = 90th centile) in mean platelet volume was found in 14 out of 15 pre-eclamptic patients between 24 weeks and 38 weeks of gestation and in only 13 of 428 normal pregnant individuals. Platelet numbers were decreased by > or = 50 x 10(9)/l (i.e. to less than the 10th centile) in 12 of the 15 patients with pre-eclampsia. 10% of the normal pregnant population showed a similar decline in platelet numbers showing that changes in platelet numbers may be a less accurate assessment of the development of pre-eclampsia.

We suggest that longitudinal determination of platelet volumes may be of use in identifying those women at risk of pre-eclampsia.