It depends on your doc with checking your cervix. Mine leaves that decision to me but did say last time that if I went over, he would check (or if I was concerned). I would just as soon be left alone so I didn't opt for it and the first time I was checked for dilation was at my admission to l&d since I went in to labor the day before my due date.
The only reason I would get another ultrasound at this point (close to you) is if he can't feel the head in my pelvis or there is some other reason for concern.
unless they suspect baby is rather large or small or suspect a problem depending on your insurance you.may not get another u/s.... and most drs start to check for dialation when you being to go weekly at 36 weeks
I believe they start checking you cervix at 36 weeks (not 100% sure). I'm 29 weeks and my doctor said I won't get another ultrasound unless it's medically needed. So you may not.