Are you able to change midwives at all?? I had a similar thing happen this time round. Measured 30cm at 26w, then a whopping 35cm at 29w so got sent for a scan which was the next week (fluid levels were normal) and I only measured 33cm at 30 and have now averaged out to 37cm at 36w. I have a bubba that refuses to drop at all!! I had a bigger baby first time round but they were only concerned if there was excess fluid around the baby. So don't worry too much, maybe baby had a growth spurt and things will average out over the next month or so. Good luck for your VBAC - you can do it.
We posted at the same time. lol

I think they do have growth spurts....but remember someone saying up until about 18 weeks they all grow at the same rate....but babies are little people so are all individuals!!!