Prior research by the author showed that psychosocial factors distinguished complicated from uncomplicated birth outcome. The purpose of this study was to determine if prenatal hypnosis could facilitate uncomplicated birth. Following a psychosocial assessment, 520 pregnant women in their first or second trimester of pregnancy were randomized to receiving prenatal hypnosis or attention-only groups. The author provided all of the hypnosis in a manner similar to that taught by David Cheek. The goal was to reduce fear of birth and parenthood; to reduce anxiety; to reduce stress; to identify specific fears that might complicate the labor process (addressing them whenever possible); and to prepare women for the experience of labor. The attention-only group was matched to a no-contact comparison group. Women receiving prenatal hypnosis had significantly better outcomes than women who did not. Further assessment suggested that hypnosis worked by preventing negative emotional factors from leading to an complicated birth outcome. Attention only was associated with minimal differences in outcome over the no-contact group. The routine prenatal use of hypnosis could improve obstetric outcome.