Does the size of the baby have anything to do with when u may go into labor?

they say that if your first was early its likly youe second will, im 31 weeks pregnant with my 3rd, both my 1st 2 were 2 weeks early and health and good size. now im 31 weeks and babys measuring 3 weeks bigger due to the charts in your note, but not sure how much he weights, i asked if its possible for him to be born early and midwife said a good possiblitie and his head was down from 28 weeks. hope this helps and good luck.xx