The majority of American soldiers undergoing amputation for war wounds last fall lost more than one limb, according to data presented Tuesday to the Defense Health Board, a committee of experts that advises the Defense Department on medical matters.

Military officials had previously released data showing that amputations, and especially multiple-limb losses, increased last year. The information presented to the 20-member board is the first evidence that the steepest increase occurred over the last four months of the year.

In September 2010, about two-thirds of all war-theater amputation operations involved a single limb (usually a leg) and one-third two or more limbs. The split was roughly 50-50 in October and November. In December, only one-quarter of amputation surgery involved only one limb; three-quarters involved the loss of two or more limbs.

The Marines, who make up 20 percent of the forces in Iraqand Afghanistan, were especially hard hit. Of the 66 wounded severely enough to be evacuated overseas in October, one-third lost a limb.

In the first seven years of the Iraq and Afghanistan wars, about 6 percent of seriously wounded soldiers underwent amputation.

Wounds to the genitals and lower urinary tract - known as genitourinary injuries - accounted for 11 percent of wounds over the last seven months of 2010, up from 4 percent in the previous 17 months, according to data presented by John B. Holcomb, a trauma surgeon and retired Army colonel.

The constellation of leg-and-genital wounds are in large part the consequence of stepping on improvised explosive devices - homemade mines - and are known as "dismounted IED injuries."

The data were assembled by Holcomb and two physicians at Landstuhl Regional Medical Center in Germany, where all seriously injured soldiers are taken on their way back to the United States.

The steep increase in both the rate and number of amputations clearly disturbed both Holcomb and members of the board, which met at a Hilton hotel near Dulles International Airport.

Holcomb, who spent two weeks at Landstuhl in December and is a former head of the U.S. Army Institute of Surgical Research, said he had heard of "unwritten pacts among young Marines that if they get their legs and genitals blown off they won't put tourniquets on but will let each other die on the battlefield."

Richard H. Carmona, who was U.S. surgeon general from 2002 to 2006 and is now on the board, said the information was "very disturbing."

He said it has made him ask: "What is the endgame here? Is the sacrifice we are asking of our young men and women worth the potential return? I have questions about that now."

Carmona, 61, served as an Army medic in Vietnam before going to college and medical school. He has a son who is an Army sergeant and is serving in Iraq.

Jay A. Johannigman, an Air Force colonel who has served multiple deployments as a trauma surgeon, said his stint at the military hospital at Bagram Airfield in Afghanistan last fall "was different" both personally and medically.

"We see the enormous price our young men and women are paying. It should not be for naught," he said. He didn't want to elaborate.

Why amputation-requiring injuries increased so much in recent months isn't entirely understood. It is partly a function of tactics that emphasize more foot patrols in rural areas. Some people have speculated the mines may be constructed specifically to cause the devastating wounds.

"Do the Marines know? Probably," said Frank Butler, a doctor and retired Navy captain who has spearheaded improvements in battlefield first aid over the last decade. "But they're not releasing a thing. And they shouldn't."