i just found this...
About a third of these, or one in about 300 women, suffer from secondary recurrence miscarriage (SRM) - the loss of three or more pregnancies after a successful pregnancy.
Dr Henriette Svarre Nielson and colleagues at the University Hospital of Copenhagen presented findings of the new study at the annual European Society of Human Reproduction and Embryology conference in Prague yesterday.
Dr Nielsen said she believed that cells that pass through the placenta from a male foetus to the mother can increase the likelihood of her immune system rejecting later pregnancies.
"We observed that most of the women we were seeing in the clinic with recurring miscarriages who had previously had normal babies had boys.
"It is known that when a woman carries a male baby it can appear as strange to her immune system, and that up to 22 years later you can still find cells from her son's immune system in her body.
"We think that there is an immune response against genes from the male Y chromosome."
Dr Nielsen added that in at-risk women it was likely that the immune reaction triggered by a protein found on the surface of male cells was boosted to the point where it could later increase the chances of the body rejecting female foetuses too.