The effects of support for women during labor and delivery provided by health professionals, lay women, and doulas on the maternal and neonatal outcomes have been evaluated through randomized clinical trials, meta-analyses, and systematic reviews. This article presents a review of these studies, focusing on the principal characteristics, support provider, simultaneous presence of the woman's spouse and/or family members during labor and delivery and the outcomes. The analysis included studies published from 1980 to 2004 which explicitly approached these aspects. In general, the results of such support were favorable, highlighting a reduction in the cesarean rate, analgesia/ medication for pain relief, duration of labor, and utilization of oxytocin and an increase in maternal satisfaction with the experience. The benefits were greater when the support provider was not a health professional. The available studies did not evaluate the specific companion chosen by the woman as a support provider, which constitutes a gap in the knowledge that should be filled by future research.