Using females as suicide bombers is another indicator of how desperate insurgents and especially Al Qaeda has gotten. The use of female bombers by Muslim extremist has been nearly unheard of until Al Qaeda in Iraq started to get desperate.
While this isn't the norm for AQI, the use of female suicide bombers by Muslim extremists isn't new. The Tamil Tigers, Chechen Black Widows, PKK, PIJ and SSNP have all used female suicide bombers with varying degrees of success. The SSNP was doing it in the 80's in Lebanon. The Tamil Tigers probably had one of the more high profile attacks with the assasination of Rajiv Gandhi. A picture of Gandhi with the LTTE bomber just prior to the attack is commonly used as a training point on perceived threats. Though it's possible that desperation is driving this latest development, I'm hesitant to to look at AQI's use as anything more than an enemy that is adapting their TTPs to a changing environment.