I think it's a bit of both, but more our bodies.

I went 8 days over with DD1
7 days over with DD2
But had DS 2 days early.

I refused to go over again & did everything I could to get him out! Well mostly walking & lots of house work. It worked though!

Hollye - It's usually only first babies that engage - go lower into the pelvis before labour. 2nd & others usually don't engage til labour.