Available data suggest that low dose aspirin may be a safe, widely available and inexpensive intervention that may significantly reduce the risk of preterm birth. However, this possibility needs to be proven in a properly designed randomized controlled trial (RCT) with preterm birth as the primary outcome. Such a clinical trial in a racially, ethnically and geographically diverse population could best be accomplished by the established infrastructure of the Global Network for Women's and Children's Health Research (GN).