No experience of my own kids coming early but my sister had first DS 5 weeks early, 2nd DS 3 weeks early and 3rd DS was 3 weeks early too (I think) so you never know, maybe time for you before you know it!
Im trying to reassure myself - they say no 2 pregnancies are the same. My ds1 came on time and no 2 was due yesterday - Im already going mad but keep trying to rationalise with myself that its normal. Midwife didnt help by telling me that this one would probably be a week early!
ds was 7 weeks early and while pregnant with dd i was told the baby was too big for my pelvis i panicked but she came 3 weeks early and she was 7.11lbs,i'm pleased she came that bit earlier but i don't know if it happens to everyone that after having an early baby the others are too