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Procedure. Components of the biophysical profile. Amniotic fluid index (AFI)
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Procedure
1. A non-stress test should be performed for a minimum of 20 minutes prior to the administration of Oxytocin.
2. Nipple stimulation:
• instruct the woman to rub one nipple through her clothing with the palmar surface of her fingers rapidly, but gently, for two minutes;
• stop for five minutes and assess uterine activity;
• if the desired contraction pattern is not achieved, instruct the woman to proceed with a second cycle of two minutes of stimulation;
• if contractions remain insufficient, bilateral nipple stimulation may be considered;
• should nipple stimulation fail to induce contractions that meet the test criteria, Oxytocin infusion should be started.
3. Establish a primary IV line (usually with normal saline).
• Prepare a secondary IV with Oxytocin 30 IU diluted in 500 mL IV solution. Connect the IV with the Oxytocin solution into the port closest to the insertion site.
• Attach the IV Oxytocin line to the infusion pump.
• Start the Oxytocin infusion at 0. 5 milliunit (mU)/ minute to 1 mU/ minute.
4. The uterine activity and the fetal heart rate are monitored with a CTG, as the uterus is stimulated to contract by the Oxytocin. The amount of solution infused is increased as necessary (it should be doubled no more often than every 20–30 minutes) to cause the uterus to contract for 30 to 40 seconds three times every 10 minutes. The fetal heart rate is observed for variability and for the timing of any marked variation from the normal in relation to uterine contractions. Decelerations of the fetal heart rate in certain repeating patterns may indicate fetal distress.
Interpretation
The OCT/CST will be interpreted using the following criteria:
• negative (normal): no late or significant variable decelerations, there are 3 contractions /10 minutes, each contraction lasts 40 seconds, no late decelerations;
• positive: repetitive, persistent late decelerations following 50% or more of contractions (even if contractions are fewer than three in 10 minute window).
Sometimes additional criteria are applied:
• equivocal-suspicious: intermittent late decelerations or significant variable decelerations;
• equivocal - hyperstimulatory: fetal heart rate decelerations that occur in the presence of contraction more frequent than every two minutes or contractions that last longer than 90 seconds;
• unsatisfactory: fewer than three contractions in 10 minute window.
Biophysical profile
The biophysical profile (BPP) is a noninvasive test to assess fetal condition. The BPP combines data from 2 sources: ultrasonographic imaging and fetal heart rate (FHR) monitoring. Dynamic realtime B-mode ultrasonography is used to measure the amniotic fluid volume (AFV) and to observe several types of fetal movement. The FHR is obtained using cardiotocograpny.
A BPP is commonly done in the III trimester of pregnancy, usually at 32 to 34 weeks, though may be done earlier. Some women with high-risk pregnancies may have a BPP test every week or twice a week in the III trimester.
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The biophysical profile includes the following:
• Amniotic fluid index
• Fetal tone
• Gross body movements
• Breathing movements
• Non-stress test.
In some forms of the BPP, placental grading (placental development or ripening) is also included.
The biophysical profile helps to diagnose intrauterine fetal distress before the beginning of labor. It is necessary to use biophysical profile in complex with other methods of investigation in choice of treatment and mode of delivery (natural ways, cesarean section, etc).
Components of the biophysical profile
Amniotic fluid index (AFI)
Ultrasonographic assessment of amniotic fluid has important implications because documentation of abnormalities of amniotic fluid volume may provide valuable information to enhance fetal health assessment. Decreased amniotic fluid volume is associated with IUGR, premature rupture of the membranes (PROM), postdatism, some major congenital anomalies, abdominal pregnancy, and excessive use of prostaglandin synthetase inhibitors. Decreased amniotic fluid volume may sometimes be due to hypoxia-induced reflex redistribution of cardiac output to the most vital organs, the heart and brain, with shunting of flow away from the amniotic fluid-producing organs, the kidneys and lungs.
AFI measurement:
• uterus is divided into 4 imaginary quadrants with linea nigra and umbilicus acting as the vertical and the horizontal axis respectively;
• the deepest pocket devoid of umbilical cord and fetal parts is measured in the vertical dimension;
• all 4 pockets are measured in centimeters and is summed, the sum of all four quadrant measurements is the AFI;
• Normal AFI values vary from 5 to 25 cm.
A single 2 cm x 2 cm pocket is considered adequate or AFI greater than 5. 0 cm.
Fetal tone (FT) - one or more episodes of extension of a fetal extremity or trunk with return to flexion, or opening or closing of a hand. Fetal tone is defined by active extension and flexion of the fetal limbs, trunk, or hand; or if the hand remains in a flexed position during the entire 30-minute test. Basically, it's an indication of how well the baby is oxygenated. Studies showed, that when FT was absent on the last BPP before delivery, the incidence of fetal distress in labor, low 5-minute Apgar scores, and perinatal mortality were much higher than if FT was present.
Gross body movements (GBM), or fetal movements (FM)
Definition: At least three discrete body or limb movements. Episodes of continuous movement are considered as a single movement.
Maternal perception of fetal movement is one of the first signs of fetal life and is regarded as a manifestation of fetal wellbeing. The normal fetus is active and capable of physical movement, and goes through periods of both rest and sleep. Hypoxic or otherwise compromised fetuses may not move as much as healthy fetuses. A significant reduction or sudden alteration in fetal movement is a potentially important clinical sign. It has been suggested that reduced or absent fetal movements may be a warning sign of impending fetal death. Studies of fetal physiology using ultrasound have demonstrated an association between rate of fetal movement and poor perinatal outcome. Real-time ultrasound assessment of fetal movements is used in diagnosis of fetal well being.
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Breathing movements (BM), fetal breathing movements (FBM)
Definition: One or more episodes of rhythmic fetal breathing movements of 30 seconds or more within 30 minutes. Hiccups are considered breathing activity. Fetal breathing movements are episodic and irregular, interspersed with periods of apnea, and in humans they become detectable by ultrasound at 10-11 weeks gestation. They are not true breathing, but they are movements of breathing musculature with closed glottis. The fetus, which develops within a fluid-filled amniotic sac, relies on the placenta for respiratory gas exchange rather than the lungs. While not involved in fetal oxygenation, fetal breathing movements (FBM) nevertheless have an important role in lung growth and in development of respiratory muscles and neural regulation. Prominent distinctions of FBM include its episodic nature and apnea-sensitivity to hypoxia. The latter characteristic is the basis for using FBM in the assessment of fetuses at risk for hypoxic injury.
Each of the four ultrasound parameters and the nonstress test are given a score of 0 or 2 points (no 1 point), depending upon whether specific criteria are met (Table 8).
Table 8
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