The non-stress test is usually taken during the third trimester, typically within one month of the expectant mother's due date.The non-stress test is often used when a pregnancy is considered high risk or has lasted past the due date, or when an ultrasound shows that uterine conditions may not be optimal.The test allows your healthcare provider to evaluate your baby's well-being by measuring changes in his heart rate.on-stress test results are available immediately. Results are considered normal, or reactive, if the fetal heart rate accelerates normally in response to movement. A non-reactive test means that the heart rate does not respond as expected.