BERLIN — Allyson Felix and Sanya Richards each won a second gold medal at the world championships today when the United States won the women's 4x400-meter relay.

Felix, the 200 champion, ran the second leg while 400 champion Richards took the baton home in 3 minutes, 17.83 seconds.

Felix won three gold medals at the 2007 worlds in Osaka, Japan, but she was unable to defend her gold in the 4x100 relay when the American team was eliminated in the heats.

Jamaica took silver in 3:21.15, and Russia earned bronze in 3:21.64.