One thing I could think of from Filipino culture is the manananggal (rough translation: one who removes). It's a sort of humanlike being, but with wings and a very long tongue. At night, its body from the waist up would fly away and leave its lower half behind, then it would hunt for food. It would go on top of pregnant womens' rooftops and using its long tongue it would feed on the fetus. Once the manananggal gets back to its lower half, the fetus would be gone forever.

In order to get the fetus back, you can prevent the manananggal from returning to its lower half by putting something on the lower half, if you find it (not sure if it was salt or garlic or something else).

One interesting thing that I'm not sure is quite related, but if you have a miscarriage, people say that 'nakunan ka' (rough translation: you were taken from / x was taken from you). Could be left over from the idea that the manananggal takes fetuses?