I think 28 weeks is probs the standard, but my midwife has twice had to reschedule my appointments for a week later because one of her clients went into labor. So each time our schedule got pushed a week, and we just went with it because everything seems peachy keen in my womb. My next appointment is 30ish weeks (barring other ladies in labor), and I'm guessing after that it'll be every two weeks, then probably every week starting at 36?
Re: When is your last monthly appt. before switching to bi weekly?