Women might start getting weekly or twice weekly get a nonstress testing after 28 weeks if you have a high risk pregnancy. (Before 28 weeks, the test isn't accurate.) Some may only need one isolated NST if the baby is not moving well.he NST can reassure you that your baby is healthy and getting enough oxygen. It's called a nonstress test because the test wonât bother your baby. Your doctor won't use medications to make your baby move.