Your obstetrician really has two patients: you and your baby. Your doctor can ask you how you are feeling and perform a variety of tests to determine your well-being, but the best way to determine how well your baby is faring in your uterus is by performing a non-stress test.
A non-stress test can be performed at anytime during your pregnancy when your doctor or midwife has some concerns, or around weeks 41 or 42 if you have not yet given birth. It is usually performed in your doctor's or midwife's office, is painless and safe for you and your baby. During the test an external fetal monitor is attached to your belly to record your baby's heart rate and you are asked to signal your doctor when you feel the baby move.
The heart rate of a healthy baby accelerates by about 15 beats per minute with movement. If a baby's heart rate does not increase during a 40 minute test period, this suggests that the baby's health may be in jeopardy. While a reactive non-stress test (baby moving with an accelerated heart rate) tells the doctor the baby is probably healthy, a nonreactive non-stress test (no acceleration of heart rate with baby's movement) may be a false alarm at least 75 percent of the time. The baby may be sleeping or just not in the mood to kick around during the testing time period. Rest assured, if there is no activity during the test, as soon as you leave the doctor's office and head home your baby will probably start kicking in every direction and putting on a show (this is known as the Murphy's Law of Pregnancy).
Another type of non-stress test is the Fetal Acoustical Stimulation or Vibroacoustic
Stimulation Test. This test evaluates the reaction of the baby to sound or vibrations and has been found to be more accurate than the traditional non-stress test.
Many doctors and midwives ask their patients to regularly record how many kicks, pokes, and other movements they feel over the course of one hour. Though this method is not foolproof, it can provide some indication of a baby's condition and can be used to screen for possible problems. If you don't notice adequate activity, your doctor will usually perform one of the more scientific non-stress tests.