The non-stress test and fetal breathing movements are suppressed when the pH falls below 7.2. If the fetal pH falls below 7.10, fetal tone and fetal movements are abolished (Vintzileos, 1987). The cumulative effect of repetitive hypoxemia is progressive oligohydramnios and fetal growth restriction. Hence, the presence of oligohydramnios with all of the other variables of the biophysical profile being normal may reflectchronic uteroplacental insufficiency.

There is a delay in central nervous system development with growth restriction. Hence, the distribution of fetal breathing movements, fetal movements and fetal eye movements (an assessor of fetal state) are different than in control fetuses. These differences are particularly striking when there is an absence of diastolic flow in the umbilical artery (Rizzo 1987).

Table I. Components of the 30 minute Biophysical Profile Score
Component Definition
Fetal movements > 3 body or limb movements
Fetal tone One episode of active extension and flexion of the limbs; opening and closing of hand
Fetal breathing movements

>1 episode of >30 seconds in 30 minutes
- Hiccups are considered breathing activity.

Amniotic fluid volume A single 2 cm x 2 cm pocket is considered adequate.
Non-stress test 2 accelerations > 15 beats per minute of at least 15 seconds duration.
Table II. Distribution of Biophysical Profile Scores
Score Description Percent
8 - 10 Normal 97.52
6 Equivocal 1.72
4 Abnormal 0.52
2 Abnormal 0.18
0 Abnormal 0.06
Derived from: Manning FA et al. Am J Obstet Gyncol 1985;151:343.
Table III. Perinatal Mortality and the Biophysical Profile Score
Score Perinatal Mortality/1000
8 - 10 1.86*
6 9.76
4 26.3
2 94.0
0 285.7
  *0.8/1000 for structurally normal fetuses with a normal test within 7 days

Derived from:
Manning FA et al. Am J Obstet Gynecol 1990;162:703.
Manning FA et al. Am J Obstet Gynecol 1985;151:343.
Manning FA (ed): Fetal Assessment: Principles and Practices. Norwalk CT, Appleton and Lange 1995, p 221.

Table IV. Maternal and Fetal Causes of Stillbirth within one week of a normal Biophysical Profile Score
Maternal Placental abruption
Diabetic ketoacidosis
Sickle cell crisis
Drug overdose
Motor vehicle accident
Acute myocardial infarction
Acute alcohol poisoning
Fetal Fetomaternal hemorrhage
Cord prolapse
Ruptured membranes
Vase previa
Cord entanglement
Umbilical artery thrombosis
Derived from: Dayal AK et al. Am J Obstet Gynecol 1995; 181:1231-1236.
Result Interpretation Risk
of Asphyxia*
Risk of Fetal
Death (per
Recommended Treatment
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
5-10 (estimate) 20-30 If mature (>37 wk), deliver
If immature, serial testing
(twice weekly)
6/10 (normal AFV) Acute asphyxia
0 50 If mature (>37 wk), deliver
If immature, repeat test in 24 h
and if <6/10, deliver
6/10 (decreased AFV) Chronic asphyxia with
possible acute
>10 >50 Factor in gestational age
If >32 wk, deliver
If <32 wk, test daily
4/10 (normal AFV) Acute asphyxia likely 36 115 Factor in gestational age
If >32 weeks, deliver
If <32 wk, test daily
4/10 (decreased AFV) Chronic asphyxia with
acute asphyxia
>36 >115 If >26 wk, deliver
2/10 (normal AFV) Acute asphyxia almost
73 220 If >26 wk, deliver
0/10 Gross severe asphyxia 100 100 If >26 wk, deliver
*Umbilical venous blood pH less than 7.25