If a corpus luteum cyst ruptures, what happens to the pregnancy?

Depends: The corpus luteum produces Progesterone which "supports" the lining of the uterus during an early pregnancy. We now know that the placenta can pretty much "take over" the function of the corpus luteum earlier than was thought. A simple serum Progesterone test can tell. If the result is 25 or greater, there should be no problem. But this depends on the rest of your history.