Lots of times, you only get one at the beginning and the anatomy one around 20 weeks. I had some later with my son bc they were afraid he was too big.
It depends on the Dr office...my doctor's office only does a 20wk and 30wk with a low risk pregnancies... Though with both of my daughters I had 4
But it also depends on your insurance and how many they cover
I have 1 probably every 2 months so that ends up being about 5 .