What the Test Does. The nonstress test is a simple, noninvasive way of checking on your baby's health. The test records your baby's movement, heartbeat, and contractions. It notes changes in heart rhythm when your baby goes from resting to moving, or during contractions if you're in labor.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.