Biophysical Profile
What is a biophysical profile?
A biophysical profile is a simple ultrasound-based test used during pregnancy to assess your baby's well-being. It is done in the third trimester to assess whether or not your baby is receiving enough oxygen. It may be considered worthwhile if:- You have diabetes, high blood pressure or some other medical condition which could affect your baby
- You go past your due date
- Your baby appears to be small or not growing
- Your baby is less active than normal
- You have an abnormality found on ultrasound examination
- You have previously had an unexplained stillbirth or a previous small baby
What's the procedure like?
- A detailed ultrasound examination during which the sonographer will observe your baby's body movements, muscle tone (position of flexion or extension at rest), and breathing movements (the baby's ability to move his chest muscles and diaphragm), and the amount of amniotic fluid. It takes about 30 minutes but it may take less time if the baby demonstrates all of the activities described in quick succession.
- A CTG (cardiotocograph) test to assess whether your baby's heart rate changes when he's moving. For this, you sit comfortably on a couch and have two transducers in contact with your tummy for about 20 minutes. One monitors your baby's heartbeat (cardio), the other records contractions in your uterus (toco). You will be asked to press a button when you feel a fetal movement. It is then recorded on a graph while you read a magazine and relax.
What do the results mean?
Each of the five components - body movements, muscle tone, breathing movements, amniotic fluid, and heartbeat - is assigned a score of either 0 (abnormal) or 2 (normal). These scores are added up for a total score ranging from 0 to 10. In general, a total score of 8 or 10 is normal, 6 is considered borderline, and below 6 is worrisome.If all the ultrasound scores are normal, your practitioner may decide not to do the heart-rate evaluation (CTG). If the results are borderline you may be asked to have something to eat and come back for it to be reassessed.
If the score is very low then your obstetrician or midwife will consider other factors (such as the baby's size and whether you have other complicating conditions) and then decide whether to deliver the baby, or whether to wait and monitor the baby with a biophysical profile or Doppler studies until it improves or gains some weight or some maturity.
Fetal Biophysical Profile Scoring
| Biophysical Variable |
Normal (Score = 2) |
Abnormal (Score = 0) |
|||
| Fetal breathing movements | 1 or more episodes of >20 s within 30 min | Absent or no episode of >20 s within 30 min | |||
| Gross body movements | 2 or more discrete body/ limb movements within 30 min (episodes of active continuous movement considered as a single movement) | <2 episodes of body/limb movements within 30 min | |||
| Fetal tone | 1 or more episodes of active extension with return to flexion of fetal limb(s) or trunk (opening and closing of hand considered normal tone) | Slow extension with return to partial flexion, movement of limb in full extension, absent fetal movement, or partially open fetal hand | |||
| Reactive FHR | 2 or more episodes of acceleration of >15 bmp* and of >15 s associated with fetal movement within 20 min | 1 or more episodes of acceleration of fetal heart rate or acceleration of <15 bmp within 20 min | |||
| Qualitative AFV | 1 or more pockets of fluid measuring >2 cm in vertical axis | Either no pockets or largest pocket <2 cm in vertical axis | |||
Reference: Manning, 1999
A 3D image of a fetus with normal tone.
The scientific basis of Biophysical Profile Scoring
When a baby becomes low in oxygen it interferes with brain activity and this affects fetal heart rate (FHR) patterns, fetal movement, and tone, in both animals and humans. Low amniotic fluid volumes can result from decreased fetal urine production. This is seen with low oxygen levels too, because blood flow in the baby is redistributed away from the fetal kidneys in favour more vital organs such as the brain, heart and adrenal glands.However, there are other reasons which can cause a low score on the day. Fetuses naturally have sleep-wake cycles which mean that they may not demonstrate active fetal movements for up to 20 minutes, normally. So the fetus has to be examined long enough to account for these normal behaviours.
Recommended Fetal Treatment According to the Biophysical Profile Score
| Result | Interpretation (Score = 2) |
Risk of Asphyxia* (%) |
Risk of Fetal Death (per 1000/wk) (Score = 0) |
Recommended Treatment (Score = 0) |
|||
| 10/10 | Nonasphyxiated | 0 | 0.565 | Conservative | |||
| 8/10 (normal AFV) |
Nonasphyxiated | 0 | 0.565 | Conservative | |||
| 8/8 (NST not performed) | Nonasphyxiated | 0 | 0.565 | Conservative | |||
| 8/10 (decreased AFV) | Chronic compensated asphyxia | 5-10 (estimate) | 20-30 | If mature (>37 wk), deliver immature, serial testing | |||
| 6/10 (normal AFV) | Acute asphyxia possible | 0 | 50 | If mature (> 37 wk), deliverIf immature, repeat test | |||
| 6/10 (decreased AFV) | Chronic asphyxia with possible acute asphyxia | >10 | >50 | Factor in gestational ageIf >32 wk, deliverIf <32 wk | |||
| 4/10 (normal AFV) | Acute asphyxia likely | 36 | 115 | Factor in gestational ageIf >32 wk, deliverIf <32 w | |||
| 4/10 (decreased AFV) | Chronic asphyxia with acute asphyxia likely | >36 | >115 | If >26 wk, deliver | |||
| 2/10 (normal AFV) | Acute asphyxia almost certain | 73 | 220 | If >26 wk, deliver | |||
| 0/10 | Gross severe asphyxia | 100 | 100 | If >26 wk, deliver | |||
*Umibilical venous blood pH less than 7.25
Reference: Manning
Reliability of the Biophysical Profile Score
The biophysical profile (BPP) is a reliable method of predicting fetal survival. Data have been collected on this and other ante-partum testing procedures for more than 20 years. Testing methods usually are evaluated by comparing the false-negative mortality rate for each method. The false-negative mortality rate is defined as the number of fetal deaths, corrected for lethal congenital anomalies and unpredictable causes of demise, that occur within 1 week of a normal test result. 'The BPP has a false-negative mortality rate of 0.77 deaths per 1000 tests. Furthermore, the BPS correlates well with the fetal umbilical venous cord pH level and neonatal outcomes. If you would like more information, please talk to your doctor or midwife or the obstetricians at Ultrasound Care when you have your test.
