Haha midwives. It's the gravity of the moon pulling on the babies! I have also heard this as well, and it's just really funny!

Sounds to me like it's just one of those things that's totally unquantifiable.

You know how women's periods sync up? That must be pretty hard to quantify but it totally happens! I've had at least 3 pregnancy scares because my ovaries decided to make play dates with those of various former roommates.