Of the 4 million annual births in the United States, 2.4 million involve epidural analgesia. Serious adverse events are rare but are important in young women. Robust estimates for the risk of harm are not available. Data for superficial and deep infections, hematoma, and transient and permanent neurologic injury were obtained from studies reporting adverse events with obstetric epidural analgesia, and incidence presented as individual risk for a woman, number of events per million women, and percentage incidence. A total of 1.37 million women received an epidural for childbirth, reported in 27 articles. Most information (85% of women) was in larger (> 10,000 women) studies published after 1990, with risk estimates as follows: epidural hematoma, 1 in 168,000; deep epidural infection, 1 in 145,000; persistent neurologic injury, 1 in 240,000; and transient neurologic injury, 1 in 6,700. Earlier and smaller studies produced significantly higher risk estimates for transient neurologic injury plus injury of unknown duration.