lol I feel like im the same Teni!

my mums third was the trouble maker...(SROM at 18weeks, on hospital bedrest for 3 months, and had him at 34 weeks - which after all that trouble she didnt even know she was in labour it was the nurses who picked it up and she was lucky to make it to the birth room in time, so was very quick).

In my work ive noticed a similar pattern...

but! like you said there is no hard and fast rule!!