Antepartum Testing Health Article

Modified biophysical profile (MBPP)

The MBPP is performed in the same manner as the NST with a limited ultrasound (US) performed to assess the amount of amniotic fluid, which is reported as the amniotic fluid index (AFI). Following the NST, an US is done to observe the amount of amniotic fluid present in four quadrants, which are divided along the umbilicus midline and perpendicular to the midline. There must be no fetal parts or any umbilical cord present in any of these pockets of fluid in order to be counted.

Contraction stress test (CST) and oxytocin contraction stress test (OCT)

The contraction stress test (CST) is similar to the NST except the FHR is evaluated for accelerations, 15 beats higher than baseline lasting 15 seconds, and in response to contractions as well. A CST requires the presence of three uterine contractions (UCs) within a 10-minute period lasting at least 40 seconds and of moderate intensity. During a contraction, the blood flow to the baby is temporarily restricted, which provides a form of "stress" to the baby. The baby's response to this stressor reveals significant information regarding available oxygen stores. If contractions are not spontaneously present, the pregnant woman will be instructed on the use of nipple stimulation to produce contractions through the release of natural oxytocin, or oxytocin can be administered through an intravenous infusion (IV) called pitocin to produce contractions. When oxytocin is administered IV, it is called an oxytocin contraction stress test (OCT). The CST/OCT is generally used after an abnormal NST is obtained in order to verify if there are problems present. Many clinicians require their diabetic patients to have at least one CST/OCT a week to assure fetal well-being. Maternal blood pressure is taken with each test.

Biophysical profile (BPP)

The biophysical profile (BPP) is performed by an ultrasound exam over a 30-minute period. The ultrasonographer/examiner looks for gross fetal movement, i.e., kicking and moving around; fetal tone, i.e., making a fist; breathing movements (which the mother can often perceive as hiccoughs); and amniotic fluid volume. A score of 0 or 2 points is assigned to each observation with the results of the NST also adding 2 points for a total possible score of 10 points.

Doppler flow studies, amniocentesis, cordocentesis, and fetal echocardiography

A physician or specially trained ultrasonographer performs Doppler flow studies, which examines the blood flow in the umbilical artery and the baby's middle cerebral artery. An experienced obstetrician/perinatologist performs the amniocentesis or the cordocentesis. For the amniocentesis, an US is used to determine an appropriate place to insert a needle and withdraw amniotic fluid for testing. In a similar manner, US is used with cordocentesis, but in this procedure a needle is guided into the umbilical cord to withdraw fetal blood for testing. Fetal echocardiography is a specialized ultrasound of a baby's heart. Since it detects most congenital heart defects, it is recommended if a baby is at a higher risk for a defect than the risk in the general population. The majority of health insurance companies do cover a portion, if not all, of the tests' costs.

Precautions

Clinicians should only prescribe these tests if they are ready to intervene when faced with worrying results. A fetus is considered viable at 24 weeks since that is the minimum gestational age for sufficient lung development. There are no significant risks to the mother or the fetus from the nonstress test (NST), modified biophysical profile (MBPP), or the biophysical profile (BPP). Ultrasound waves utilized in detecting the FHR and for the BPP are painless and safe because this method employs no harmful radiation. There is no evidence that sound waves cause any harm to the mother or the baby.

Aftercare

If the test results are acceptable, the pregnant woman is instructed to continue following her current medical regimen and return for additional testing on the dates prescribed. For NSTs/MBPPs/CSTs, the time period between tests should be no longer than three to four days under high-risk conditions with fetal movement counting taking place in between testing dates. Ultrasounds should be rescheduled as the need dictates per the physician. Electronic fetal monitoring occurs after an amniocentesis or cordocentesis to assure fetal well-being.