Marit Wold was born in Oslo, and won her first of 13 national championships in the relay with her club Kjelsås IL in 1985. Her last came in 1999, and later that year she gave birth to her first daughter. Wold had her international breakthrough in 1988, when she was Norwegian champion at 20 km, earning a place on the Calgary team, where she won an Olympic relay silver medal. Ten years later, in Nagano, Wold won another relay silver medal, while at Lillehammer in 1994, she won her only individual Olympic medal, placing second in the 30 km classical. At the 1997 World Championships in Trondheim she won a bronze medal at the same event. In addition, she won two World Championships relay silver medals, in 1995 and 1997.
In 1994 Wold married Norwegian skier Pål Gunnar Mikkelsplass, and from the 1994-95 season competed under her married name. She won six individual Norwegian Championships from 1988-97 and won the women’s class at the 1996 Birkebeiner. She finished her nursery studies in 1998, and then gave birth to two daughters in 1999 and 2002. Her family settled in Nes in Buskerud county, where Marit Mikkelsplass worked as the head of nursing care in the municipality.