Out of interest, at how many weeks were each of your DC born?
For me:
DS1 at 40+5
DS2 at 36 +5 (so caught me by surprise to say the least!) No apparent reason for him being so early.
Am pregnant with no 3 and can't help musing when it might come. Of course I know no-one can actually say, but I did wonder if others had also had first one overdue and second early, whether no 3 tended to follow the first or the second?