Expanding the horizons of perinatal research: Randomized trials in the fields of education and health services

The randomized controlled trial is the most rigorous research design for evaluating the effectiveness of an intervention. The key feature of this design is the assignment of study participants to one treatment or another through a system analogous to flipping a coin. Through this random assignment of the study sample to groups, both known and unknown determinants of outcomes are distributed in an unbiased manner, which thereby minimizes the possibility of biased study results. In addition to the random assignment of subjects to groups, the central foundations of a rigorous, randomized controlled trial include the definition of a clear and specific problem, a precisely defined study population from which a sample is drawn, exposure of all members of the experimental group to the same intervention, protection of the control group from any such exposure, prevention of any other factors from unequally affecting either group, compliance of study participants with treatment group assignment, and reproducible and accurate measurement of the outcome. The power of the highquality, randomized controlled trial lies in its ability to establish an association between intervention and outcome and to eliminate all others. Traditionally, the randomized controlled trial has been used to evaluate drug interventions. In a drug trial, a specified number of patients who meet defined eligibility criteria are randomized to take either the drug of interest or a placebo identical to the experimental drug in size, color,