Numerous heavy crashes have marred the women's Olympic luge competition in Cesana on Monday.
Retrosi slid down the track under her sled after crashing at Cesana
US luger Samantha Retrosi was taken to hospital with concussion and short-term memory loss after sliding under her sled for at least two corners.
Italy's Anastasia Oberstolz-Antonova, Ukrainian Natalia Yakushenko and Czech Marketa Jeriova also crashed out.
Luge veteran Anne Abernathy, 52, dubbed "Grandma Luge", broke her wrist in a training spill on Sunday.
Racing was suspended for 20 minutes and screens erected as medics attended Retrosi, who span out of control at the end of her second run.
"It was a bad crash. But the bottom line is that she's going to be OK," said US team leader Fred Zimny.
The accidents will revive fears about the daunting Cesana Pariol course, which had to be closed for modifications soon after its opening last year when four sliders ended up in hospital.
Abernathy, from the US Virgin Islands, was looking forward to her sixth Olympics but was forced to pull out.
She made history in 2002 by becoming the oldest woman to compete at the Winter Games at the age of 48.
The previous oldest women's competitor was Canadian Edwina Chamier, who was 45 when she took part in the Alpine skiing combined event in 1936.
Abernathy was not the only 52-year-old entered at the Olympic luge competition.
Werner Hoeger, 52, a university professor from Venezuela, came 32nd in the men's singles competition on Sunday.
The oldest competitor of the Turin Games is the 54-year-old Scott Baird, an alternate in the American men's curling team.