system
Given the following post, respond as if you're commenting on Reddit:
human
What are the physiological processes in a woman's body responsible for inducing and performing the expulsion of a fetus during a miscarriage?

I understand an early miscarriage is often induced by a chromosomal abnormality, but how does the body know there is a chromosomal abnormality? And then how does the body proceed to expel the fetus? Is it just the fetus "falling out" or does the body intentionally and actively push out the fetus? If the latter, what are the physiological processes involved and how do they work?
gpt
Once the fetus is connected to the woman's body via the placenta it starts sending out chemical signals. These cause the woman's body to suppress her immune system, interupt her normal fertility cycle, and have various other effects. 

If the fetus is not viable, it is unable to emit these chemical signals for one reason or another. Once the fetus stops sending signals, the woman's immune system and normal fertility cycle will attack/expell the fetus. But this is not a perfect system and a lot can go wrong, causing the woman to need medical intervention with a miscarriage, especially later in pregnancy.