Jacobs took second place in the 1500 m race at the 6th World Championships in Athletics in Athens (4:04.63) in 1997, and again won the silver medal in the 1500 m at the World Championships in Sevilla in 1999 (4:00.35). In her years of running she won 25 national titles. On February 1, 2003, at age 39 Jacobs set a world record in the indoor 1500 m with a time of 3:59.98, becoming the first woman to break 4 minutes in the event. Jacobs remains the only American woman to run under 4 minutes in the indoor 1500 meters and stands as the USATF American Indoor record holder in 2015. Regina's 2 mile record was broken by Jennifer Simpson in 2015.