Aspirin in the prevention of preeclampsia: the conundrum of how, who and when.

Aspirin is widely used in preventing early onset preeclampsia in women who are identified as being high risk. Although the benefit of aspirin is increasingly evident and acknowledged, there remains many unanswered questions with regards to its optimal application in pregnancy. The issues mainly centre around the relatively modest risk reduction that is observed with the use of aspirin prophylactically. We aim to explore the reasons behind the conservative rate of benefit and aim to explore factors that are likely to influence the outcomes with the use of aspirin.