An "immune clock" of pregnancy could guide future researchers as they explore ways to prevent disorders like preterm birth.

Clinical trials are crucial to developing lifesaving drugs and procedures, but medical researchers today are frustrated: Often benefits from the proposed advances are so subtle that they require increasingly complex and incredibly expensive studies involving thousands of patients to show whether or not there is some small benefit. At the same time, patients are pressing for access to promising treatments as soon as possible, sometimes before the trials are even done.