The ABC news story on this suggests that women may be targeted as a strategy.
http://abcnews.go.com/US/IraqCoverage/story?id=878703&page=1June 24, 2005 -- At least six Marines, three of them female, were killed after a suicide bomber rammed into their military vehicle Thursday night in Fallujah, Iraq, ABC News has confirmed.
The military said in a statement that two Marines were killed and 13 wounded, 11 of them women. If confirmed, it would be the largest one-day casualty count for women serving in the military since the start of the war in Iraq.
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At least 1,730 members of the U.S. military have died since the war began in March 2003, with 44 women among the casualties.
While every servicemember's death, regardless of gender, is a loss, targeting female troops may be the latest attempt to shock and destabilize U.S. forces. It was not clear whether this was an intentional attack on female troops, but many recent suicide attacks have targeted civilians, including women and children.