A deficiency in a protective hormone may be behind some early miscarriages, preliminary research suggests. The hormone, called corticotropin-releasing hormone (CRH), is normally released by the mother and the embryo soon after it implants itself in the womb. Without it, the embryo may be left vulnerable to attack from the mother's immune system.
CRH triggers the production of a protein called Fas ligand (FasL) that keeps maternal immune system cells from attacking the embryo. Without CRH, these cells would go after the embryo as if it were a virus or other foreign invader. Indeed, half of the genetic material of an embryo is foreign to the mother's body, as it came from the father. And the new findings from experiments with rat and human cells suggests that some women who cannot sustain a pregnancy may be unable to control these immune reactions.
The study showed that CRH is produced by the early embryo and plays a major role in the implantation of the embryo in the endometrium of the mother. It appears that fetal or endometrial CRH deficiency could be associated with infertility or early miscarriage.