It also acts to actually suppress the immune system of the mother. So remember, what the immune system does is it basically attacks any foreign object that is found inside our body. And technically speaking, the fetus as well as our placenta are two foreign objects. And so what this hormone does is it suppresses the maternal immune system, the mother's immune system, to ensure that the immune cells do not actually attack the placenta or the growing fetus. Now, the human corianic Tropin is produced strictly and only by our placenta, by the mother's placenta. And what that means is one way we can test whether or not a woman is pregnant is by testing the blood level of this hormone found inside the woman's blood.