Objective: To determine whether aspirin therapy in women at risk of pre-eclampsia alters in vitro platelet aggregation.
Design: Longitudinal observational study.
Setting: RPMS Institute of Obstetrics and Gynaecology, Hammersmith Hospital, London.
Subjects: Six pregnant women at-risk or with pre-eclampsia.
Methods: Women considered to be at risk of pre-eclampsia or with the disorder were treated with aspirin. In vitro platelet aggregation in response to platelet-activating factor (PAF) and adenosine diphosphate (ADP) before and after aspirin therapy were analysed.
Results: Prior to aspirin therapy platelet aggregation was decreased compared with normal pregnant women. After aspirin therapy platelet aggregation in response to PAF and ADP was greater, but did not return to levels associated with normal pregnancy.
Conclusions: In women with pre-existing decreased platelet aggregation suggestive of platelet exhaustion, aspirin increased aggregation. This suggests that aspirin decreases in vivo platelet activation and thereby decreases the platelet exhaustion revealed by the in vitro studies.