Nonstress Test. A nonstress test is used in pregnant women to evaluate the heart rate of a developing baby (fetus). Normally, a developing baby 's heart rate ranges from 100 to 160 beats per minute, and it usually speeds up after the baby moves.If the heart rate is faster or slower than this range or does not speed up after the baby moves, it may mean that the baby is not doing well. During the test:ormally, a developing baby 's heart rate ranges from 100 to 160 beats per minute, and it usually speeds up after the baby moves. If the heart rate is faster or slower than this range or does not speed up after the baby moves, it may mean that the baby is not doing well. During the test: