Gestational age and fetal biophysical assessment

With improved neonatal care, biophysical assessment to detect fetal asphyxia is used increasingly at an earlier gestational age. We have tested five fetal biophysical variables: nonstress test, fetal breathing movements, fetal movements, fetal tone, and amniotic fluid volume 11,012 times in 5582 singleton fetuses in whom there was a normal perinatal outcome. The nonstress test and fetal breathing movements were more likely to be abnormal at 26 to 33 weeks' gestation compared with 34 to 41 weeks. The nonstress test, fetal breathing movements, fetal tone, and amniotic fluid volume were more likely to be abnormal at 42 to 44 weeks' gestation compared with 37 to 41 weeks. Fetal biophysical tests should be interpreted in relation to gestational age.     

Prognostic components of computerized fetal biophysical testing

Fetal biophysical testing with arbitrary scores for fetal heart rate (FHR), breathing movements, body movements, tone, and amniotic fluid volume has not proved to be highly sensitive or significantly better than FHR testing alone. Using a computerized analysis system for simultaneously acquired biophysical variables, we studied 200 high-risk fetuses near term. The dynamic parameters obtained for each fetus were compared with established nomograms, and overall test results correlated with the presence or absence of perinatal mortality, fetal distress, a 5-minute Apgar score less than 7, and intrauterine growth retardation for those delivered within 7 days of the last test. A test was considered abnormal if two or more parameters fell more than 2 standard deviations from the population mean. A decreased incidence of fetal body movements, amniotic fluid volume, and frequency of FHR acceleration were the most common individual test abnormalities. Test sensitivity (86%), specificity (89%), positive predictive value (75%), and negative predictive value (93%) exceeded those of the "standard" scoring approach and correctly identified all fetuses with malformation, perinatal death, and 19 of 22 fetuses with intrauterine growth retardation.     

Fetal breathing movements: antepartum monitoring of fetal condition.

Until recently, the relative inaccessibility of the human fetus to physical assessment has made antepartum assessment of its condition difficult. The development of methods for accurate antepartum fetal heart rate monitoring and the subsequent study of heart rate responses to various stimuli have resulted in a significant improvement in accuracy of antepartum fetal surveillance. The development of real time B-mode ultrasound enables the clinician to assess many additional fetal biophysical variables including fetal breathing movements. In our observations, the combination of heart rate and fetal breathing assessment has produced a significant improvement in differentiating the normal from the compromised fetus. The addition of other biophysical variables (tone, movements and amniotic fluid volume) have further refined the ability to identify the fetus at risk. At this point, we have evaluated only a few of many possible variables. It seems probable that, as other fetal biophysical variables are included with the overall assessment, for example fetal reflexes or fetal biophysical response to exogenous stimuli, the identification of the fetus at risk and the quantitation of the magnitude of risk will become increasingly more precise.     

The biophysical profile in multiple pregnancy

The high risk attributed to multiples calls for close observation during pregnancy. Based on adequate predictions in singletons, it was expected that the biophysical profile (reactive fetal heart rate pattern on non-stress test, presence of fetal breathing and body movements, documentation of normal fetal tone and adequate amount of amniotic fluid) could be used in multiples as well. However, the paucity of studies could not demonstrate an equivalent predictive capacity in multiple pregnancies.     

Sinusoidal heart rate pattern and an normal biophysical profile in a severely compromised fetus

A case is described in which a woman complained of weakened fetal movements, and a persistent sinusoidal heart rate pattern was demonstrated in the presence of normal fetal breathing movements, normal fetal tone, and normal amount of amniotic fluid. In view of the subjective complaints and disregarding the normal biophysical profile, termination of pregnancy was performed. A compromised, severely anemic fetus was delivered by cesarean section. The role of sinusoidal heart rate pattern and the limitations of biophysical scores as a single determinant of fetal well being are discussed.     

The fetal biophysical profile in pregnancies with grade III placentas

The components of the fetal biophysical profile of pregnancies with grade III placentas and good outcome were retrospectively analyzed and compared to the fetal biophysical components of pregnancies with grade 0 to II placentas. The results of the present study suggest that the dynamic components of the fetal biophysical profile (nonstress test, fetal breathing movements, fetal movements, fetal tone) are not altered in the presence of a grade III placenta and good pregnancy outcome; however, a greater incidence of reduced amniotic fluid volume was found in the presence of grade III placenta. The clinical significance of grade III placenta is discussed.     

Modified fetal biophysical profile in the assessment of perinatal outcome

The aim of the study is the evaluation of variables of the biophysical profile in the assessment of perinatal outcome. The prospective study included 87 pregnant women with singleton pregnancy in the 28th to 42nd week of gestation with clinically and ultrasonically verified fetal growth retardation, where the fetal biophysical profile was assessed antenatally. Through the factor analysis of biophysical profile variables we obtained values indicating the contribution of individual variables to the predictability of perinatal outcome. 70% of the patients were examined in 15 minutes according to the principles of modified biophysical profile. The most sensitive variable of the biophysical profile in the prediction of perinatal outcome was the amniotic fluid volume, followed by fetal breathing movements, non-stress test and fetal movements, while the lowest prediction value was assigned to the fetal tone. The modified biophysical profiles need to be perfected on a larger number of pregnant women, which would advance the predictability of this method in detection of hypoxically endangered fetuses.     

The fetal biophysical profile in patients with premature rupture of the membranes--an early predictor of fetal infection

A modified fetal biophysical profile (nonstress test, fetal movements, fetal breathing movements, fetal tone, amniotic fluid volume, and placental grading) was serially assessed in 73 patients who presented with premature rupture of the membranes and were not in labor. The last study before delivery was compared with the outcome of pregnancy. The relationships between individual variables and combinations of variables (biophysical scoring) and the outcome of pregnancy--as reflected by the development of chorioamnionitis and/or neonatal sepsis--were determined. These data suggest that the fetal biophysical profile is a useful tool for evaluating patients with rupture of the membranes. Rupture of the membranes by itself does not alter the biophysical scoring of the healthy fetus; however, a low biophysical score (less than or equal to 7) was a good predictor of impending fetal infection in patients with premature rupture of the membranes.     

Relationship Between Combined Fetal Biophysical Activities,Oligohydramnios, and Fetal Acid–Base Status

The purpose of this study was to determine the relationship between combined fetal biophysical activities, oligohydramnios, and fetal acid-base status at the time of testing. In a prospective study of 101 patients undergoing cesarean section before the onset of labor, a fetal biophysical profile was performed within 3 h before the cesarean section. Different combinations of fetal biophysical activities (fetal heart rate reactivity, fetal breathing movements, fetal body movements, and fetal tone) and oligohydramnios were correlated with umbilical cord blood gas and acid-base measurements (artery and vein). Fetal acidemia was defined as umbilical arterial blood pH <7.20. The group of fetuses with reactive nonstress test (NST) and/or fetal breathing present had significantly higher pH, pO₂, bicarbonate, and base excess and significantly lower pCO₂ levels compared with fetuses who had nonreactive NST, absent fetal breathing, and compromised or absent body movements and tone. These blood gas and acid-base differences were observed in both umbilical cord artery and vein. There was a significant relationship between oligohydramnios and fetal acidemia. Seven of 15 (46.6%) fetuses with oligohydramnios were acidemic and 7 of 15 (46.6%) acidemic fetuses had oligohydramnios (P = 0.0008). Fetuses with compromised or absent movements and tone had the highest incidence of acidemia (10 of 11 or 91%) and oligohydramnios (4 or 11 or 36%). The presence of oligohydramnios was associated with increased frequency of acidemia in every combination of biophysical activities. However, when all biophysical activities were absent, the frequency of acidemia was 100% regardless of the presence or absence of oligohydramnios. In conclusion, progressive loss of fetal biophysical activities is associated with increasing frequency and severity of fetal acidemia and oligohydramnios.     

Fetal biophysical profile in twin gestations

The fetal biophysical profile (nonstress test, fetal breathing movements, fetal movements, fetal tone, amniotic fluid volume, placental grading) was assessed in 49 consecutive referred high-risk patients with twin gestations. The relationship between the last fetal biophysical profile score before delivery was compared with the pregnancy outcome--as reflected by the presence of fetal distress and perinatal death. These data suggest that the fetal biophysical profile is a useful tool for observing fetal status in patients with twin gestations, and could be reliably used as a means of follow-up of nonreactive nonstress testing in these patients.     

Fetal biophysical profile and the effect of premature rupture of the membranes

A retrospective study of 1151 fetal biophysical profiles and scores associated with good pregnancy outcome was conducted over a three-year period in the author's institution. Normal fetal biophysical activities and scores were determined throughout gestation from 25 to 44 weeks in patients with intact membranes, and compared with profiles and scores of a group of patients with premature rupture of the membranes and good pregnancy outcome. These data suggest that although the biophysical scoring of the healthy fetus with intact membranes does not change significantly throughout gestation, some of the fetal biophysical variables (nonstress test, fetal breathing movements, amniotic fluid volume, and placental grading) do. The rupture of membranes was found to be associated with higher incidence of reactive nonstress testing, absence of fetal breathing, and reduced amniotic fluid volume in most gestational ages; however, the overall biophysical scoring of the healthy fetus was not altered throughout gestation by the presence of ruptured membranes.     

The effect of magnesium sulfate tocolysis on the fetal biophysical profile

The biophysical profile has proved to be a valuable tool for the assessment of fetal well-being, independent of gestational age. Magnesium sulfate is commonly used as a tocolytic agent, yet relatively little is known about its effects on the biophysical activities of the fetus. To investigate the effects of magnesium sulfate on the biophysical profile, we performed serial studies on patients who received tocolytic therapy with this agent because of preterm labor. A total of 16 women with 22 fetuses at 26 to 34 weeks' gestation in spontaneous preterm labor were studied. An initial biophysical profile was performed at the time of admission, and a second examination was performed when maternal serum magnesium levels reached 6 to 8 mg/dl. On admission all fetuses had reactive nonstress test results and 21 of 22 (95%) demonstrated sustained fetal breathing movements. With magnesium sulfate tocolysis, 50% of fetuses had nonreactive nonstress test results, and only 4 of 22 (18%) demonstrated sustained fetal breathing movements. Fetal tone, gross body movements, and amniotic fluid volume were found to be unaffected by magnesium sulfate tocolysis.     

The abnormal fetal biophysical profile score. V. Predictive accuracy according to score composition

The relationship between last abnormal biophysical profile score, in total and by variable composition, and a spectra of abnormal perinatal outcome end points was examined in 525 fetuses. Highly significant inverse relationships between last test score and outcome were observed; relationships were linear for most end points and exponential for perinatal mortality end points. For biophysical profile scores less than or equal to 6, 25 of the 26 possible variable combinations were observed, at varying frequencies. For a biophysical profile score of 6, the positive predictive accuracy for some end points was significantly higher with either nonreactive nonstress test/fetal tone absent or nonreactive nonstress test/absent fetal breathing movement, and significantly lower with absent fetal breathing movement and decreased amniotic fluid volume. For a biophysical profile score of 4, the positive predictive accuracy for some end points was significantly higher with nonreactive nonstress test/absent fetal breathing movement/decreased amniotic fluid and was significantly lower with absent fetal movement/fetal breathing movement/fetal tone. No significant variation was observed for a biophysical profile score of 2. These data indicate that not all abnormal biophysical profile scores are equal.     

Fetal body and breathing movements as predictors of intraamniotic infection in preterm premature rupture of membranes

A prospective study of fetal behavior in cases complicated with preterm premature rupture of membranes was conducted in 41 patients. The length of time and the number of fetal breathing and gross body movements were correlated with the amniotic fluid culture results. An episode of fetal activity (body movements and breathing movements) of greater than or equal to 30 seconds during 30 minutes of observation was associated with the absence of intraamniotic infection in 100% of the cases. On the other hand, the absence of fetal breathing movements and gross body movements of less than a 50 second duration during 30 minutes of observation was associated with positive amniotic fluid cultures in all cases. If an episode of fetal breathing movements was present but lasted less than 30 seconds and/or the total time of gross body movements was greater than 50 seconds, 64% of patients had an intraamniotic infection.     

Human fetal breathing: associated changes in heart rate and beat-to-beat variability

A computerized quantification of fetal heart rate and beat-to-beat variability was performed during and between fetal breathing episodes. Sixteen healthy pregnant women at term participated in the study. The results indicate that fetal breathing is associated with a significant increase in beat-to-beat variability (from 4.48 +/- 1.66 between breathing episodes to 5.80 +/- 2.04 during breathing episodes, p less than 0.01) and a small but significant decrease in fetal heart rate (from 142.7 +/- 8.6 bpm between breathing episodes to 140.4 +/- 8.6 bpm during breathing episodes, p less than 0.05).     

Precipitated opiate abstinence in utero

Following direct infusion of morphine (0.6 to 80.0 mg/hr) to the fetal lamb for 2 to 6 hours, naloxone administration precipitated a fetal abstinence syndrome consisting of desynchronization of electrocortical activity; increased total body movements, neck tone, and eye movements; continuous rapid, deep breathing movements; immediate bradycardia associated with transient increases in systolic, diastolic, and pulse pressures; and meconium staining of the amniotic fluid. This syndrome resembles that observed in the opiate-abstinent human neonate.     

Abnormal nonstress test yet otherwise reassuring biophysical profile in a compromised fetus with severe antepartum intracranial hemorrhage

The fetal biophysical profile (BPP), a widely accepted modality of assessment of fetal well-being, significantly shortens the time required to document reassuring fetal testing and exhibits lower false-positive and false-negative rates than conventional nonstress testing. We describe a case in which a patient presenting for fetal testing due to suspected fetal growth restriction at 29 weeks of gestation with recent onset of decreased fetal movements exhibited a concerning nonreactive nonstress test. BPP assessment revealed active fetal tone, movements, breathing movements and amniotic fluid volume (BPP score 8/8). Despite the reassuring BPP, continued abnormal nonstress testing led to subsequent abdominal delivery of an acidotic infant with evidence of a massive antepartum intracranial insult consisting of frontal intraparenchymal hemorrhage and a right temporal-occipital cortical infarction. This case exhibits limitations of the BPP.     

Longitudinal measurements of fetal breathing, body movements, heart rate, and heart rate accelerations and decelerations at 24 to 32 weeks of gestation

Fetal breathing, fetal body movements, fetal heart rate, and fetal heart rate accelerations and decelerations were studied longitudinally in healthy fetuses between 24 and 32 weeks' gestation in the second and third hour following an 800 kcal maternal meal. The expected increase in fetal breathing following a maternal meal was not seen until fetuses were at 30 to 32 weeks' gestation. The number of body movements decreased and the interaction between body movements and fetal heart rate accelerations became more evident as fetuses became older. Fetal heart rate decelerations increased with gestational age, and the relative proportion of total decelerations that were either associated with body movements or were part of a deceleration/acceleration/deceleration complex increased from 24 to 32 weeks' gestation. The data support the hypothesis that gestational age is an important variable to consider when interpreting biophysical measurements in the human fetus at 24 to 32 weeks' gestation. Fetal body movements may be the single most important measurement of fetal health at these gestational ages.     

The effect of magnesium sulfate on the behavioral activities of fetal goats

OBJECTIVES: To investigate fetal heart rate accelerations, fetal breathing movements, and fetal electrocortical activities during administration of magnesium sulfate to fetal goats. METHODS: The fetal heart rate accelerations, fetal breathing movements, and fetal electrocortical activities during 6 hours of continuous magnesium sulfate infusion into the fetal jugular vein were examined in 8 chronically instrumented fetal goats at 124-131 days of gestation. Fetal breathing movements were defined as repetitive negative fluctuations of the fetal tracheal pressure. Fetal electrocortical activities were assessed by visual analysis of periods of high-voltage and low-voltage electrocortical activities. RESULTS: Continuous infusion of magnesium sulfate for 6 hours significantly increased the fetal plasma magnesium concentration from 2.8 +/- 1.2 to 8.3 +/- 2.6 mg/dL without significant changes in fetal arterial blood gases. The incidence of fetal heart rate accelerations during magnesium infusion was significantly decreased from that found during the control periods. After 2 hours of infusion, the incidence of fetal breathing movements significantly decreased from 33.9% +/- 20.5% to 1.2% +/- 1.4% and remained at this level during the remaining 4 hours of magnesium infusion. The percentage of time that the fetuses were found to have low-voltage electrocortical activities decreased from 51.6% +/- 9.0% to 40.4% +/- 8.2% after 2 hours of infusion but recovered to 49.9% +/- 12.0% by 6 hours of magnesium infusion. CONCLUSION: We concluded that fetal magnesium sulfate administration affected fetal heart rate accelerations and fetal breathing movements continuously but electrocortical activities only temporarily during 6 hours of observations.     

Real-time ultrasound observation of breathing and movements in the fetal lamb

In seven pregnant ewes with catheters chronically implanted in the fetus, real-time ultrasound observations of fetal breathing and body movements were correlated with direct measurements of fetal arterial and tracheal pressures, heart rate, and intrauterine pressure. There was excellent correlation between the ultrasound record of fetal breathing and recordings of intratracheal pressure changes even when breath amplitude was low or frequently was high. Fetal body movements (stretches, rolls, kicks) were observed during both breathing and nonbreathing periods; vigorous movements were accompanied by rapid deflections of the amniotic and tracheal pressure traces. Movement was frequently accompanied by transient increases or decreases in heart rate. The results indicate that real-time ultrasound is an accurate method for observation of fetal movement in pregnant sheep and is particularly valuable when combined with direct measurements of fetal physiologic parameters.