I have not had this, but my sister-in-law does. Her first baby girl was born 3 weeks after my oldest son. Then the next 3 pregnancies were miscarriages about week 11 -13.
I do not know what the condition is, since we live 1000's of miles from them and don't see them often.
But she injects heparin into her thigh every day to keep from clotting the baby's circulatory system.
It is painful toward the end when her legs are sore but it works and keeps her immune system from over-reacting. They now have 6 (yes, 6!) beautiful, healthy children from age 17 to an one year old. She had to see 3 ob/gyn's until she found the one who could help her.