Fetal pulse oximetry: a clinical methodological study

The aim of the study is to provide preliminary assessment of the possibilities of fetal pulse oximetry as a method for monitoring of fetal pulse rate and oxygen saturation during labour. The study includes 65 pregnant women during active labour at term--all with one fetus and ruptured membranes. A system for fetal pulse oximetry is used, consisting of monitor Nellcor-N 400; oxygen sensor FS-14 and printer P-400 (Nellcor Puritan Bennett incorporation). Sensor is applied by mean dilatation of cervical channel 6.5 +/- 1.9 cm. Mean duration of monitoring of the pregnant woman is 104 +/- 68 minutes, range 30 to 180 min. The time of reliable signal quality is 83% for first stage of labour and 70% for second stage of labour. Mean SpO2 values are 47.1 +/- 9.8%. The conclusion is made that fetal pulse oximetry is an easy method to use, without side effects for mother and fetus. Mean SpO2 values are tower than in adults and vary inside wider range 35-55%.     

The effect of umbilical cord encirclement on fetal arterial oxygen saturation values

AIM: Our purpose was to study fetal arterial oxygen saturation trends by continuous pulse oximetry during labour in subjects with and without umbilical cord encirclement. MATERIAL AND METHODS: The study was carried out in 46 pregnant women in the 38.9 +/- 1.4 weeks of pregnancy and the 15 of them with umbilical cord encirclement, established respectively after delivery. The fetus was monitored continuously with an Oxford S 8000 system and pulse oximeter Nellcor N-400. The medium parameters of FSpO2 values during progressive stages of labour in both groups were shown. The importance of the correlation was assessed using the t-Student's table of N--2 degree of freedom. RESULTS: In those two groups no significant difference between FspO2 value in first stage of labour was found. In second stage of labour our study showed tendency for higher oxygen saturation values in foetuses without umbilical cord compression.     

Fetal oxygen saturation during labour

Objective To derive oxygen saturation by pulse oximetry (SpO₂) values at each cervical dilatation in labour in fetuses with normal neonatal outcome.
Participants One hundred and forty-five women at term in established labour with ruptured membranes and cervical dilatation at least 2 cm who had normal delivery outcome. The infants had 5 minute Apgar scores 7, birthweight 2500 g, umbilical cord artery pH 7.15 and did not require assisted ventilation or admission to neonatal intensive care.
Methods Women were monitored continuously with cardiotocography and fetal pulse oximetry using the Nellcor N-400 fetal pulse oximeter and FS-14 fetal oxisensor till delivery. Labour was managed according to established protocol without recourse to SpO₂ readings.
Results There was a wide range of SpO₂ values during labour hi fetuses with normal outcome. Mean values averaged 50%±10% throughout the first stage of labour, with lower ranges of SpO₂ values above 30%. There was no significant difference in SpO₂ readings at different cervical dilatations in the first stage of labour. Mean SpO₂ values in the last 10 minutes before delivery were also not significantly different from those in the first stage of labour.
Conclusion The range of SpO₂ in 115 healthy fetuses during normal labour was wide, but always above 30%. There was no trend of SpO₂values in this study of 115 fetuses with normal neonatal outcome.     

Intrapartum oxygen saturation in fetus with symptoms of distress shown during fetal cardiotocograph monitoring

The aim of the study is to establish the mean values of SpO2, during labour with symptoms of fetal distress and to find out when fetal hypoxia is expected to develop as well as unsatisfactory clinical status of the newborn. The study includes 62 women on labour at term with pathological decelerations from the fetal heart rate (FHR). SpO2 is monitored by means of fetal pulse oxymeter Nellcor N 400. Simultaneously FHR is monitored by means of cardiotocography. Fetal well-being is verified by pH u blood gas analysis from fetal scalp while the newborn well-being is proven by pH from umbilical artery and Apgar score at minute 1 and 5 after birth. The mean continuity of SpO2 recording during the first period of labour is 107.84 +/- 25.77 min., with mean 86.74 +/- 7.06% reliability of the recordings; for the second period--26 +/- 8.98 min. with reliability of the recordings 77.07 +/- 9.96%. During the first period of labour the mean value of SpO2 is 43.00 +/- 6.75%. With dilation of 4-5cm SpO2 is 46.25 +/- 5.92%, with 6-7CM SpO2 is 44.43 +/- 6.39% and with 8-9cm dilation SpO2 is 42.69 +/- 6.80%. During second period of labour the mean value of SpO2 is 39.14 +/- 8.41%. There is a statistically significant fall of SpO2 during the second period compared to the first period of labour (p<0.05). A correlation exists between the values of SpO2 and the well-being of the newborn and a fall of SpO2 equal or less than 30% is a sign of developing abnormal condition of the newborn.     

The management of labor overweight women with intrapartum fetal oxygen saturation monitoring

OBJECTIVE: Overweight is one of the most common problems that occurs in pregnancy. The aim of this study was to evaluate the usefulness of fetal pulse oximetry during labour and to compare fetal oxygen saturation between cases with pregravid overweight and normal weight. MATERIAL AND METHODS: Fetal oxygen saturation was continuously recorded with use of Nellcor N-400 fetal pulse oximeter in 20 cases of pregravid overweight and 30 control cases of normal weight. Distribution of fetal oxygen saturation values during 4 periods of labour was analyzed and compared between the examined groups together with neonatal umbilical artery pH values, Apgar score, birth weight and percentage of ceasarian sections performed. RESULTS: We noticed statistically important differences in fetal oxygen saturation between analyzed groups. Mean oxygen saturation value was lower in the overweight group, at the end of first stages of the labour (47% vs 52%) and at the second stages (42% vs 46%) We noticed differences in birth weight too. No significant differences in neonatal umbilical artery pH, ceasarian sections, newborns mean 1 minute Apgar score were observed between analyzed groups. CONCLUSION: Fetal pulse oximetry is a a useful method for intensive surveillance of the fetus at risk of hypoxemia during the labour. A lower fetal oxygen saturation value during labor by pregravid overweight were observed.     

Use of oxi-cardiotocography in twin delivery

The intrapartum management of multiple gestation continues to challenge the obstetrics profession. Electronic fetal heart rate monitoring and fetal pulse oximetry are used in clinical research to assess fetal well-being during labor. The objective of this study was to establish values of fetal arterial oxygen saturation (FSpO2) and some other parameters by dint of computerised analysis of cardiotocogram during twin delivery. 5 cases of vaginal twin deliveries as the Clinic of Perinatology of the Institute of Gynecology and Obstetrics Lodz Mecical University over the years 1988-1999 were reviewed. In four cases vertex-vertex twins were delivered vaginally, while in one case an assisted breech extraction was conducted on vertex-non vertex twins. The foetus was monitored continually with a Oxford S 8000 systems and pulse oximeter Nellcor N-400. the medium parameters of computerised analysis of CTG and FSpO2 during progressive stages of labour were shown. Twin delivery needs modern fetal monitoring tools to provide the obstetrician information on well-being of the foetus. It is possible to monitor fetal oxygen saturation and CTG parameters in both of the twins during labour The ability to measure fetal oxygen saturation especially during the second stage of twin labor adds critical information about fetal status and refines the interpretation of abnormal FHR patterns. Only after examining a large number of twin fetuses we can assess whether pulse oximetry in useful in management of labor.     

Usefulness of the pulse oximetry in diagnosis of fetal distress during labor

We report the computer control system of simultaneous monitoring of cardiotocography and pulse oximetry during labour. Five of twenty five patients have abnormal CTG results with oxygen saturation over 30%. In the three subjects severe late decelerations were related with decrease of saturation to 20%. Mean SaO2 measurements ranged from 62% at the early stage of labour to 45% in the second stage. We conclude that fetal pulse oximetry plays important complementary role among methods of intrapartum monitoring and it will be used in every case with suspicious or pathological CTGm.     

Response of fetal acid--base balance to duration of second stage of labour.

Data from 4081 vaginal deliveries (no caesarean sections) were analyzed retrospectively (IBM 730/158) with regard to duration of second and "final stage" of labour and fetal outcome (acid-base balance and apgar scores). The average duration of the two periods amounted to 22.8+/-29.6 and 9.9+/-7.8 min. Mean pH (UA) was 7.268+/-0.084 and the acidotic risk (pH less than 7.20, pH less than 7.10) 13.4 and 1.6% respectively. The distribution of the Apgar-scores after 1 min was assessed: 0-3: 1.7%, 4-6: 5.4%, 7-10: 92.9%. The dependance of the time variables from parity was studied. Two samples (N1=1755, N2=1098) of uncomplicated term pregnancies were chosen according to 7 clinical selection criteria differing only in the presence of cord entanglements at birth. The association between the two time variables and parameters of the fetal acid-base balance in cord blood was evaluated using rank correlation- and polynomial regression analysis. Highly significant correlations (tau) were found between the variable time and actual pH in blood of the umbilical artery and vein as well as pCO2, BEECF and HbO2 in the umbilical vein. The association however is not very close and thus clinically not of great importance. The deltapH (UA & UV) pro 60 min of second (and "final") stage of labour was computed and amounted to -0.024 (-0.087) in blood of the umbilical artery and -0.036 (-0.115) in blood of the umbilical vein and -0.017 (-0.062) (UA) and -0.032 (-0.120) units (UV) in the sample with and without apparent cord entanglements at birth respectively. The response of fetal acid-base balance to cord compression during second stage of labour was assesses: The acidotic risk (pH less 7.2) was doubled: 14.5% (7.7%) and AV-differences of all variables were "opened" if cordcoilings were observed. Apgar scores were not significantly different. Moreover, the association between AV-differences of each parameter and the variable time was studied: it became evident that with passage of time AV-difference is "closed" (-0.052 AV DpH/60 min "final stage" of labour, N=1098) indicating time related impairment of placental function. From these observations and data of the literature the conclusion is drawn that second stage of labour should not exceed 45 min in any patient. Furthermore it is concluded that in cases without signs of impending fetal distress it seems to be possible to wait more than 20 (Multipara) or 30 min (Primipara) duration of "final stage" without increased risk of fetal peril measured in terms of acidemia and clinical depression. This is valid only in term pregnancies with the possibility of continuous monitoring of FHR, in cases with normal uterine activity, uneventful course of first stage of labour and cooperative, vigorous patients. The indications for termination of delivery by vaginal operations in cases without impending fetal distress are discussed.     

Fetal pulse oximetry in second stage of labor

OBJECTIVE: To compare the mean values of fetal oxygen saturation with fetal heart rate pattern in the second stage of labor (Melchior classification) MATERIAL AND METHODS: The study included 30 parturients in gestational age 37-41 weeks. Fetal oxygen saturation was recorded and averaged over the last 30 min of the second stage of labor Simultaneously, fetal heart rate and uterine contractions were monitoring. Fetal heart rate patterns were assessed according to Melchior's classification. At birth, the cord acid-base parameter (pH) was calculated. RESULTS: The lowest value of fetal oxygen saturation over the last 30 min of labor was 10%, the highest 60%, and the mean value 39.1 +/- 12.5%. Statistically, significant correlation between the mean value of oxygen saturation over the last 30 min of labor and pH arterial values (n = 25, p = 0.004, r = 0.42) was found. There was no statistically significant correlation between fetal oxygen saturation and pH venous values (n = 24, p. = 0.006, r = 0.49), but trend towards significance could be observed. Statistical analysis revealed that arterial pH was significantly correlated to Melchior's classification. The lowest pH and FSpO2 values coexisted with type 3 and 4 of FHR patterns according to Melchior's classification. CONCLUSIONS: The mean values of fetal oxygen saturation over the last 30 min of labor significantly correlate with arterial pH values. These values correlate with FHR abnormalities according to Melchior's classification. Fetal pulse oximetry seems to be an important, additional method assessing fetal well-being in the second stage of labor.     

Monitoring of labour and delivery in the presence of meconium stained amniotic fluid by pulse oximetry

OBJECTIVES: Evidence of meconium-stained amniotic fluid during labor suggests implementation of close monitoring of fetal well-being. DESIGN: Our purpose was to compare fetal oxygen saturation between cases with normal and meconium stained amniotic fluid. MATERIALS AND METHODS: Fetal oxygen saturation was continuously recorded with use of Nellcor N-400 fetal pulse oximeter in 30 control cases of term labour of normal, and 30 cases of meconium stained amniotic fluid. Distribution of fetal oxygen saturation values during 5 periods of labour was analyzed and compared between the examined groups, and presented in forms of Tables, together with neonatal umbilical artery pH values, Apgar score, birth weight and percentage of caesarian sections performed. RESULTS: No significant differences in fetal oxygen saturation, neonatal umbilical artery pH, birth weight and caesarian sections rate were observed between analyzed groups. Newborns 1-th minute Apgar score (mean value) and base excess was lower in meconium group compared to control group. CONCLUSIONS: Our data demonstrate, that fetal oxygen saturation trends to decrease during labour in fetuses in both groups.     

Normal values for fetal scalp tissue pH during labour.

Normal values for fetal scalp tissue pH during labour were determined by using a glass electrode (Kontron-Roche). A total of 132 recordings was obtained and 84 (64 per cent) were of good quality. After a good quality recording had been obtained, there were 64 infants with an Apgar score of 9 or 10 at one and five minutes after delivery. The 64 recordings showed pH values (Mean +/- 2SEM) of 7.38 +/- 0.12 six hours before delivery and 7.28 +/- 0.12 at the time of delivery. Between the 5th and 55th minutes of the second stage of labour the pH (Mean +/- 2SEM) fell from 7.30 +/- 0.14 to 7.20 +/- 0.13.     

Evaluation of fetal heart rate patterns during the second stage of labor through fetal oximetry.

The purpose of this study was to assess the feasibility and accuracy of fetal pulse oximetry during the second stage of labor in cases with abnormal fetal heart rate (FHR) patterns with reference to postpartum acid-base status and Apgar scores. Forty-eight parturients with normal and 20 parturients with abnormal FHR tracings during the second stage of labor were monitored by fetal pulse oximetry and postpartum umbilical artery pH, pO(2), pCO(2) values and 1- and 5-min Apgar scores. The mean SpO(2) value was 55. 47 +/- 9.95% in cases with normal and 52.55 +/- 16.42% in cases with abnormal FHR patterns. A significant correlation was noted between fetal SpO(2) and umbilical artery pH in cases with normal (r = 0.76, p < 0.05) as well as in cases with abnormal FHR patterns (r = 0.78, p < 0.05). No significant correlation was found between fetal SpO(2) and Apgar scores at 1 and 5 min in cases with normal FHR patterns. On the contrary a significant correlation was noted in cases with abnormal FHR patterns. A normal FHR pattern alone is reassuring. In cases with abnormal FHR, fetal pulse oximetry is an objective method for distinguishing a hypoxic fetus.     

Intrapartum Fetal Oxygen Saturation Monitoring in Congenital Fetal Heart Block

Summary: Conventional intrapartum electronic fetal heart rate monitoring is not informative in certain fetal conditions because the electronically-monitored fetal heart rate pattern is uninterpretable in terms of reflecting fetal normoxia. Such fetal conditions include various cardiac dysrrhythmias and some central nervous system abnormalities. Difficulties with intrapartum fetal welfare surveillance in such conditions often lead to operative delivery as a precautionary measure. We report 2 cases of intrapartum fetal oxygen saturation monitoring in the presence of congenital complete heart block (CCHB), using the Nellcor N400/FS14 oxygen saturation monitoring system. Mean intrapartum fetal oxygen saturation (FSpO₂) was 32% (SEM ± 1%) in the first case and 48% (SEM ± 0.3%) in the second case. In both cases, vaginal delivery of otherwise healthy infants was achieved. Fetal pulse oximetry is a promising new technique which directly measures fetal oxygenation without reference to fetal heart rate patterns. It may assist in the intrapartum fetal welfare assessment in conditions such as complete heart block, thereby helping to avoid otherwise unnecessary operative delivery.     

The usefulness of the intrapartum fetal pulse oximetry in anticipating the neonatal outcome

OBJECTIVE: The aim of the study was to evaluate the usefulness of the intrapartum fetal pulse oximetry in anticipating the neonatal outcome. MATERIALS AND METHODS: The saturation of the fetal blood (SpO2) was measured during labor with non-invasive pulse oximeter designed for fetal application. The average, minimum and maximum SpO2 were evaluated separately for the first and the second stage of labor. The average SpO2 of the fetus was compared to neonatal condition assessed by umbilical vein pH, pO2 and pCO2 and according to Apgar score. RESULTS: Twenty patients have been monitored with fetal pulse oximetry. All those patients had normal vaginal delivery. During the first stage of labor, the average fetal SpO2 was 51.94 +/- 8.03%, the minimum SpO2 was 38.35 +/- 9.15%, and the maximum SpO2 was 63.35 +/- 7.75%; in the second stage of labor average fetal SpO2 was 43.82 +/- 7.16%, minimum SpO2 was 34.35 +/- 7.79% and the maximum SpO2 was 50.94 +/- 8.37%. A significant decrease in fetal average and maximum SpO2 occurred from stage I to stage II of labor (average SpO2: 51.94 +/- 8.03% vs. 43.82 +/- 7.16%, p = 0.0002; maximum SpO2: 63.35 +/- 7.75% vs. 50.94 +/- 8.37%, p < 0.00001). The significant correlation between the average SpO2 during the first stage of labor and umbilical vein pH (R = 0.60, p = 0.02) and pO2 (R = 0.54, p = 0.04) was found. No relationship between fetal SpO2 in the first and second stage of labor and Apgar score was observed. CONCLUSIONS: 1. The second stage of labor results in significant decrease in fetal SpO2. 2. The fetal SpO2 > 30% in the first and second stage of labor is related to good neonatal outcome. 3. The fetal SpO2 assessment in first stage of labor seems to be important in newborn's acidosis and hypoxemia predicting.     

The accuracy of fetal pulse oximetry in the second stage of labour

The aim of this study is to assess the accuracy of fetal monitoring with pulse oximetry at delivery. The pulse oximetry reading from the fetus at delivery was compared to fetal condition at birth. There is poor correlation between fetal scalp oximetry readings at delivery and fetal condition (Apgar scores), umbilical venous or arterial blood gas analysis or pH. Although there are good theoretical reasons why the correlation should not be perfect, the wide deviation from expected values suggest that readings taken during delivery are particularly prone to errors. Examination of the unprocessed photodetector signal during the second stage of labour reveals considerable movement interference. The signal may also be affected by congestion and transmitted venous pulsation in the scalp as the head crowns. The current generation of reflectance pulse oximeters can predict fetal hypoxemia during labour but a single reading during delivery is subject to too much movement interference to produce useful data.     

Usefulness of the examination of fetal blood oxygen saturation (FSpO2) and fetal heart rate (FHR) as a prognostic factor of the newborn outcome

OBJECTIVES: Cardiotocography has become the standard for fetal monitoring in labor. False-positive findings during electronic fetal heart rate monitoring may were not associated with neonatal acidemia. Because of the poor specificity of fetal heart rate monitoring in predicting fetal distress, new methods are being investigated as a way to improve the accuracy of assessing the infant's condition during labor. DESIGN: The aim of this study was to determinate the efficiency of fetal blood oxygen saturation (FSpO2) and computer analysis of the fetal heart rate (Co-CTG) in the late 1-st stage of labor as a prognostic factor of newborn acidemia. MATERIALS AND METHODS: Total 62 subjects were studied. During labors and deliveries fetal oxygen saturation was continuously recorded, with use of Nellecor N-400 fetal pulse oximeter and continous CTG were performed by Hewlett Packard 50A. Transdermal fetal oxygen saturation measurements and CTG results obtained during the labors was analyzed using MONAKO system (ITAM Zabrze). The results were compared with the values of pH and base deficit in the umbilical artery measured just after delivery. RESULTS: The sensitivity, specificity, negative, positive predictive values and Youden factor based on FHR and FSpO2, for prognosis of neonatal acidosis were: 65%, 80%, 16%, 97.5% 60% and 0.135 respectively FHR; and 100%, 60%, 100%, 96.8% and 0.968 respectively FSpO2. CONCLUSIONS: 1. The examination of fetal blood oxygen saturation in the labor is a useful prognostic factor of the newborn outcome. 2. The best predictive value for intrapartum fetal asphyxia with metabolic acidosis was found when fetal pulse oximetry is added to cardiotocography.     

Fetal monitoring with pulse oximetry

Summary. Continuous fetal monitoring was achieved with a fetal scalp pulse oximetry sensor in 86 labours. The average recorded fetal oxygen saturation in early labour (cervical dilatation < 5 cm) was 68% (SD 13%). At the end of labour (cervical dilatation ≥ 9 cm) the recorded mean oxygen saturation was 58% (SD 17%). The largest range of readings during a single labour was 81%-11% but this drop was associated with cord compression. The average SD during 1 h of normal labour was 10%. A second group of 40 fetuses was monitored during induction of labour before and after elective amniotomy. Oxygen saturation did not appear to change after amniotomy (mean change −0.4%, SD 1.2%) and there was no difference between mean antenatal or early intrapartum readings. We excluded the amniochorionic membranes as a possible source of data corruption by measuring their in vitro absorption spectra and confirming that they do not preferentially absorb light of either 660 or 940 nm wavelength. Non-invasive pulse oximetry can be used to monitor the fetus before and during labour.     

Multicenter study on the clinical value of fetal pulse oximetry: I. Methodologic evaluation

Objective: Our purpose was to evaluate the feasibility of intrapartum fetal pulse oximetry, the distribution of fetal oxygen saturation values, and the relationship with the neonatal outcome in a population with an abnormal fetal heart rate. Study Design: A prospective multicenter observational study was performed from June 1994 to November 1995. Fetal oxygen saturation was continuously recorded with use of a Nellcor N-400 fetal pulse oximeter in case of an abnormal fetal heart rate during labor. Simultaneous readings of fetal oxygen saturation and fetal blood analysis were obtained at inclusion and before birth. Feasibility, adverse effects, distribution of fetal oxygen saturation values, and relationship with neonatal outcome were assessed. Results: One hundred seventy-four patients were included. From 172 attempted sensor placements, the procedure was impossible in three cases and fetal oxygen saturation values were obtained in 164 cases (95.3%). Physicians considered sensor placement an easier task than an attempt at fetal blood analysis (easy in 87.5% vs 78.9% for fetal blood analysis, p = 0.03). The mean reliable signal time (±SD) was 64.7% ± 32% during the first stage. There were no serious adverse effects in the study population. The mean fetal oxygen saturation during the first stage of labor was 42.2% ± 8.0% (10th to 90th percentile range 30% to 53%). Fetal oxygen saturation was significantly correlated with scalp pH (r = 0.29, p = 0.01) but not with neonatal umbilical artery pH or gas values. There was a significant association between low fetal oxygen saturation (<30%) and poor neonatal condition. Conclusion: The feasibility of fetal pulse oximetry is satisfactory in clinical practice. It is easy to use and provides a fair rate of recorded values, even in a population with suspicion of fetal distress. A low fetal oxygen saturation is significantly associated with an abnormal neonatal outcome.     

Fetal heart rate and neonatal condition related to epidural analgesia in women reaching the second stage of labour

The relationship between epidural analgesia and a number of labour and delivery factors, relevant to fetal and neonatal condition, was considered in a prospective study of 200 labours reaching the second stage of labour. The group was representative of the hospital population with regard to the proportion of nulliparous women, the incidence of instrumental vaginal deliveries and the incidence of epidural analgesia (37%). The 8% of labours requiring fetal blood sampling during the first stage, and the labours with fetal heart rate (FHR) decelerations in the hour prior to second stage (25%) and during pushing (50%) were significantly more likely to have been given an epidural. Nulliparity (55%), induced labour (34%), a first stage longer than eight hours (37%), a second stage longer than 60 min (43%), maternal pushing for longer than 36 min (50%), forceps delivery (28%) and a 1 min Apgar score less than 7 (12%) were also factors associated with significantly higher rates of epidural analgesia whereas meconium (15%), a small baby (16%) and umbilical arterial metabolic acidaemia (13%) were not. FHR decelerations in labours reaching the second stage with an epidural reflect adjustments to fetal cardiovascular control and not acidaemia.     

Fetal Pulse Oximetry: A New Method of Monitoring the Fetus

Summary: Experimental pulse oximetry devices, similar to the existing systems used in adult and neonatal monitoring, can be used on the fetus to provide safe, and rapid information about oxygenation. They have been calibrated using fetal lambs and validated in human cross-sectional studies. Experiments have shown that fetal oxygen saturation decreases during normal labour, and drops after a uterine contraction especially with oxytocin-induced tachysystole. When the mother is given oxygen the fetal oxygen saturation increases. Readings are effected by caput and movement, and trends seem to be more meaningful than absolute values. Pulse oximetry can predict fetal outcome and a normal oxygen saturation result is specific for a good outcome perhaps even if the CTG is abnormal. However the technique is still experimental and there is insufficient data to support its use as a replacement for fetal blood sampling or a discriminator for an abnormal fetal heart trace.