I think it really varies, everyone on here has had a slightly different experience. I had a few earlier like at 27 and 28 weeks because once I didn't think the babies were moving and the other was because of PTL. I was at the peri last week at 32 weeks and that's when he had me schedule my first official NST. Now I am having them weekly until I deliver.
I think it can also vary from practice to practice or the hospital you go to. Since I had triplets, they started mine around week 23 once weekly. Then they went to twice weekly around week 27 until I delivered. Of course, once I went into the hospital I had them twice a day. :huh: But they only had to be reactive during the morning nst. Good luck and take a book to read.
They don't start them here until 30 weeks, and I think they do them weekly or bi-weekly depending on the pregnancy. Juli