Early Prediction and Aspirin for Prevention of Preeclampsia

This will be a randomized control trial to estimate the efficacy of low dose aspirin in preventing preeclampsia in women identified in the first trimester to be at high risk. We will also obtain maternal blood, cord blood and placenta specimen for basic science studies to attempt to dissect biological mechanisms of aspirin effects. In addition we will conduct a cost-benefit analysis to determine the cost effectiveness of screening and using aspirin prophylaxis for screen positive women.

Rationale for Design: The randomized control trial is the 'gold standard' of research design. Other designs such as case-control, retrospective cohort and prospective cohort are limited by potential bias and confounding. Randomly assigning subjects to different interventions minimizes selection bias. The random assignment also results in groups that are likely to be similar with regards to important confounding variables. This minimizes confounding by both measured and unmeasured factors. While random allocation does not guarantee the groups will be identical, it does ensure that any differences between them are due to chance alone. Finally, randomization produces groups that are random samples of the population. This permits use of standard statistical tests that are based on probability theory.