Fetal Scalp Blood pH Research Articles

Intrapartum Assessment of Fetal Well-being

In Brief Objective To determine whether the need for fetal scalp pH sampling is decreased by the scalp stimulation test and whether redefinition of reactivity and presence of variability further decrease the need for scalp pH sampling. Methods One hundred eight women with fetal heart rate (FHR) patterns suggestive of acidosis underwent fetal scalp blood pH evaluations. Digital scalp stimulation was performed for 15 seconds 1–2 minutes before pH sampling. The study group was subdivided based on reactivity to scalp stimulation and scalp puncture and was correlated with pH values. Reactivity was defined as an acceleration of 15 beats per minute or more lasting at least 15 seconds and redefined as an acceleration of 10 beats per minute or more lasting at least 10 seconds. Nonreactive responses were subdivided based on FHR variability preceding the scalp stimulation and were correlated with pH values. Fisher exact test was used for analysis. Results All 51 instances of acceleration of 15 beats per minute or more lasting at least 15 seconds following scalp stimulation had a scalp pH of 7.20 or more. Using an acceleration of 10 beats per minute or more lasting at least 10 seconds, seven more reactive responses were obtained after scalp stimulation, all with pH of 7.20 or more. The 15 instances in which the pH was less than 7.20 were nonreactive irrespective of the definition of reactivity (P < .001). Twenty-one of the 50 instances of nonreactive responses (reactive response: acceleration of 10 beats per minute or more lasting at least 10 seconds) had positive variability. Only two of these 21 (9.5%) instances compared to 13 of the 29 (45%) instances with negative variability had pH less than 7.20 (P < .007). Conclusions The scalp stimulation test could decrease the need for fetal scalp blood sampling by 47%. Redefinition of reactivity could decrease the need for scalp sampling by 54%. In addition, assessment of FHR variability before scalp stimulation could decrease further the need for scalp blood sampling by 73%. In suspected intrapartum fetal acidosis, a redefinition of reactivity after scalp stimulation test and assessment of variability decreases the need for fetal scalp pH blood sampling.

Intrapartum assessment of fetal well-being: A comparison of scalp stimulation with scalp blood pH sampling

To determine whether the need for fetal scalp pH sampling is decreased by the scalp stimulation test and whether redefinition of reactivity and presence of variability further decrease the need for scalp pH sampling. One hundred eight women with fetal heart rate (FHR) patterns suggestive of acidosis underwent fetal scalp blood pH evaluations. Digital scalp stimulation was performed for 15 seconds 1-2 minutes before pH sampling. The study group was subdivided based on reactivity to scalp stimulation and scalp puncture and was correlated with pH values. Reactivity was defined as an acceleration of 15 beats per minute or more lasting at least 15 seconds and redefined as an acceleration of 10 beats per minute or more lasting at least 10 seconds. Nonreactive responses were subdivided based on FHR variability preceding the scalp stimulation and were correlated with pH values. Fisher exact test was used for analysis. All 51 instances of acceleration of 15 beats per minute or more lasting at least 15 seconds following scalp stimulation had a scalp pH of 7.20 or more. Using an acceleration of 10 beats per minute or more lasting at least 10 seconds, seven more reactive responses were obtained after scalp stimulation, all with pH of 7.20 or more. The 15 instances in which the pH was less than 7.20 were nonreactive irrespective of the definition of reactivity (P < .001). Twenty-one of the 50 instances of nonreactive responses (reactive response: acceleration of 10 beats per minute or more lasting at least 10 seconds) had positive variability. Only two of these 21 (9.5%) instances compared to 13 of the 29 (45%) instances with negative variability had pH less than 7.20 (P < .007). The scalp stimulation test could decrease the need for fetal scalp blood sampling by 47%. Redefinition of reactivity could decrease the need for scalp sampling by 54%. In addition, assessment of FHR variability before scalp stimulation could decrease further the need for scalp blood sampling by 73%.

Intrapartum assessment of fetal well-being: A comparison of scalp stimulation with scalp blood pH sampling

Objective: To determine whether the need for fetal scalp pH sampling is decreased by the scalp stimulation test and whether redefinition of reactivity and presence of variability further decrease the need for scalp pH sampling. Methods: One hundred eight women with fetal heart rate (FHR) patterns suggestive of acidosis underwent fetal scalp blood pH evaluations. Digital scalp stimulation was performed for 15 seconds 1–2 minutes before pH sampling. The study group was subdivided based on reactivity to scalp stimulation and scalp puncture and was correlated with pH values. Reactivity was defined as an acceleration of 15 beats per minute or more lasting at least 15 seconds and redefined as an acceleration of 10 beats per minute or more lasting at least 10 seconds. Nonreactive responses were subdivided based on FHR variability preceding the scalp stimulation and were correlated with pH values. Fisher exact test was used for analysis. Results: All 51 instances of acceleration of 15 beats per minute or more lasting at least 15 seconds following scalp stimulation had a scalp pH of 7.20 or more. Using an acceleration of 10 beats per minute or more lasting at least 10 seconds, seven more reactive responses were obtained after scalp stimulation, all with pH of 7.20 or more. The 15 instances in which the pH was less than 7.20 were nonreactive irrespective of the definition of reactivity ( P P Conclusions: The scalp stimulation test could decrease the need for fetal scalp blood sampling by 47%. Redefinition of reactivity could decrease the need for scalp sampling by 54%. In addition, assessment of FHR variability before scalp stimulation could decrease further the need for scalp blood sampling by 73%.

Requiem for a Heavyweight

Fetal scalp blood pH sampling has played a valuable role in the development of our understanding of fetal welfare in labor and in the interpretation of electronic fetal heart rate patterns. There is question as to the feasibility of retaining this practice in modern obstetric care because of the advance of science, the general reliance on fetal monitoring criteria for ascertaining fetal well-being, the logistic difficulties involved in obtaining accurate and timely samples, the economic consequences of having to maintain analytic equipment in working order in times of very infrequent use, and the poor correlation between pH alterations and predictable neurologic consequences in the child. As it has all but vanished from use in most clinical care centers, and the principal argument for retaining it ultimately references the physician as the beneficiary, the author proposes that it should be removed from any possible association with purported “standards of care.”

Maternal factors contributing to asphyxia neonatorum

The objective was to identify maternal risk factors for birth asphyxia, and took the form of a retrospective study over 3 years of 15,964 deliveries. The antenatal and intrapartum course of 68 mothers who delivered babies with birth asphyxia was studied. Babies < 34 weeks/< or = 2000 g at birth were excluded. A 5-min Apgar score < 6 was regarded as abnormal. The incidence of asphyxia neonatorum was 4.6/1000. Most mothers (76 per cent), resided locally, booked (91 per cent), and had satisfactory antenatal clinic attendance (average seven visits). The distribution showed a disproportionately large number of grand multiparas (10 per cent). Labour was characterized by prolonged first (49 per cent) and second (36 per cent) stages with a high incidence of meconium in the amniotic fluid (47 per cent). Most deliveries (53 per cent) were by caesarian section of which 44 per cent were performed for fetal distress. Meconium aspiration was common (34 per cent). High risk signs in labour can be recognized. The judicious use of the partogram, fetal scalp blood pH, and amino-infusion are encouraged.

Scalp blood lactate: a new test strip method for monitoring fetal wellbeing in labour.

To determine fetal scalp blood lactate with a new test strip method in parturients with normal and abnormal cardiotocograms during labour and to describe the relation to maternal lactate, fetal scalp blood pH, cord artery lactate and acid-base balance. Labour wards at the University Hospitals of Huddinge and Lund and at the County Hospital of Ostersund, Sweden. Fetal scalp blood was sampled for lactate (n = 269) and pH (n = 285) determination in 177 parturients with abnormal intrapartum CTG. Lactate and pH were also analysed in a group of 64 women with normal pregnancies and with a reactive fetal heart rate tracing prior to sampling of fetal scalp blood. At fetal blood sampling lactate was also determined in maternal capillary blood, while at birth lactate and acid-base balance in cord artery blood was performed in almost all cases. Medians and percentiles (lactate and acid-base balance). Correlation between fetal scalp blood lactate (dependent) and scalp blood pH, cord artery blood lactate and acid-base parameters and labour time prior to fetal blood sampling. In the group with abnormal cardiotocograms, fetal scalp and umbilical artery blood lactate and acid-base parameters differed significantly from the same parameters in the normal group. The fetal-maternal lactate gradient changed from negative in the normal group to positive in the fetal distress group. Multiple regression analysis, with scalp lactate as the dependent parameter, revealed a significant correlation with fetal scalp blood pH (P < 0.001) and umbilical artery lactate (P < 0.01). Intrapartum scalp blood lactate was significantly correlated with pH and cord artery lactate. The results indicate that increased lactate levels in fetal blood sampling describes fetal lactacidosis. The new disposable test strip requiring only 5 microliters of blood for lactate determination may be better than traditional methods for monitoring fetal wellbeing in labour.

A multicentre comparative study of 17 experts and an intelligent computer system for managing labour using the cardiotocogram

To investigate 1. whether an intelligent computer system could obtain a performance in labour management comparable with experts when using cardiotocograms (CTGs), patient information, and fetal blood sampling and 2. whether experts could be consistent and agree in their management of labour. An intelligent computer system and 17 clinicians experienced in fetal monitoring from 16 centres in the UK. Fifty cases with complete intrapartum CTGs and clinical data were reviewed by each expert and the system independently on two occasions, at least one month apart. Each CTG was scored in 15 min segments according to a protocol and estimates of the cervical dilatation and fetal scalp blood pH were given when requested. Consistency and agreement in the recorded scores, agreement and timing of cases recommended for caesarean sections, fetal blood sampling rates, intervention in cases with poor outcome and intervention in cases with good clinical outcome. The system: 1. Agreed with experts well and significantly better than chance (67.33%, kappa = 0.31, P << 0.001). 2. Was highly consistent (99.16%, kappa = 0.98, P << 0.001) when used by two operators independently. 3. Recommended no unnecessary intervention in cases with normal delivery and good condition (cord artery pH > 7.15, vein pH > 7.20, 5 min Apgar > or = 9 and no resuscitation). This was better than all but two of the experts. 4. Recommended delivery by caesarean section in 11 cases; at least 15 of the 17 experts in each review also recommended caesarean section delivery in these cases. The majority did so within 15 min of the system and two-thirds did so within 30 min. 5. Identified as many of the birth asphyxiated cases (cord arterial pH < 7.05 and BDecf > or = 12, and Apgar score at 5 min < or = 7 with neonatal morbidity) as the majority of experts and one more than was acted upon clinically. The experts were found to be consistent and to agree. There was good agreement in the cases and the timing of caesarean section recommendations. The majority of experts did not recommend operative intervention in cases which had a normal delivery and good outcome, but did recommend operative interventions in 10 of 12 cases delivered with cord arterial pH < 7.05. However, in one of the cases delivered with birth asphyxia, 14 of the 17 experts and the system failed to recommend intervention. The system's performance was found to be indistinguishable from the experts' in the 50 cases examined, but it was more consistent. This demonstrates the potential for an intelligent computer system to improve the interpretation of the CTG and decrease intervention. Furthermore, the good performance of most experts in this study demonstrates the potential effectiveness of the CTG and raises important questions regarding why the CTG has fallen short of expectations in current practice.

Utilization of Fetal Heart Rate Acceleration Following Vibroacoustic Stimulation in Labor to Predict Fetal Acidemia and Base Deficit Levels

The absence of a fetal response to vibroacoustic stimulation (VAS) performed during labor may be an indicator of fetal acidemia. A lack of fetal heart rate (FHR) acceleration following VAS has been correlated with fetal scalp blood pH 7 mEq/L but was more sensitive to detect levels >10 mEq/L. All patients with pH 10 mEq/L. This stud...

Response of Fetal Heart Rate to Scalp Stimulation Related to Fetal Acid-Base Status

The correlation of the response of the fetal heart rate (FHR) to scalp stimulation and the acid-base status of the fetal scalp blood (FSB pH) was studied in 104 term fetuses during labor. The mean FHR was determined for the 5-minute period before the preparation for fetal scalp blood pH determination and 1 minute following FSB pH. The analysis was performed for three pH groups: (a) Normal (pH more than 7.25, = 73); (2) preacidotic (pH 7.20 to 7.25, = 16); and (3) acidotic (pH less than 7.20, = 15). The pH was confirmed at delivery by determination of umbilical cord blood acid-base status. Regression analysis of the number of fetuses responding by changing their heart rate against time was significant only for the nonacidotic fetuses. There was no significant difference in the number of subjects whose mean FHR increased, decreased, or remained unchanged between the three pH groups. Furthermore, there was no difference between the three pH groups in the number of fetuses who demonstrated significant mean heart rate changes (p less than 0.05) following the stimulation compared to those who did not. Further analysis between fetuses in the three pH groups who increased FHR 15 beats/min or more following stimulation did not discriminate between groups. We conclude that scalp stimulation results in a FHR response in all three pH categories. However, the net change in the mean heart rate following the stimulation may be negative or positive. The magnitude and the direction of this change in FHR is not significantly related to FSB pH.(ABSTRACT TRUNCATED AT 250 WORDS)

Reactive fetal heart rate response to vibroacoustic stimulation in fetuses with low scalp blood pH.

Fetal vibroacoustic stimulation in fetuses with suspicious or ominous fetal heart rate traces in labour was followed by acid-base balance determination on fetal scalp blood within 30 min of the test. The mean fetal scalp blood pH values were significantly higher in fetuses that showed reactive responses with fetal heart rate acceleration compared with those who had no response or responded with a deceleration to the vibroacoustic stimulation (pH 7.30 and 7.22 respectively). However, acidotic scalp blood pH values (7.16 and 7.18) were found in two fetuses which had shown reactive responses both to vibroacoustic stimulation and pain stimuli with scalp blood sampling.

Umbilical artery flow velocity waveforms in labour.

Doppler signals were recorded from the umbilical arteries in 103 women during labour. The pulsatility index (PI) did not alter with progress in labour. During uterine contractions the PI showed a change only if there was a deceleration in the fetal heart rate. Low birthweight (less than 10th centile) and delivery by caesarean section for fetal distress were significantly more frequent in patients with abnormal PI values (defined as greater than 2 SD above the mean in normal labours). Fetal scalp blood pH was measured in 24 patients. The PI was abnormal in only one case, but none of the 24 had a pH less than 7.20.

A study on intrauterine fetal resuscitation with terbutaline

A randomized study on the effect of terbutaline on fetal distress was carried out in 20 patients who showed evidence of ominous fetal heart rate patterns and fetal scalp blood pH values of less than 7.25. Of those, 11 received terbutaline (study group) and nine did not (control group). There was a significant improvement in the acid-base status of the fetus in the study group compared with those in the control group (p less than 0.01). No significant maternal or fetal morbidity occurred in the study group. Apgar scores at 1 minute were 7 or greater in 10 of the 11 study subjects whereas only four of the nine control subjects had a score of 7 or greater. These results suggest that terbutaline may become a useful agent in the treatment of intrauterine fetal distress.

Fetal distress during labour in diabetic pregnancy.

The frequency of fetal distress in labour was studied in 46 diabetic women and in 46 non-diabetic matched controls. Fetal distress was assessed by electronic fetal heart rate (FHR) monitoring and fetal scalp blood pH determinations in late first stage of labour. Ominous FHR and/or low pH (less than 7.26) was more common in the diabetic group than in the control group (17.4% and 10.9%, respectively) but the difference was not statistically significant. The frequency of caesarean section and low Apgar score at 1 min was significantly higher in the diabetic group (P less than 0.05). There was no correlation between maternal blood glucose regulation and the occurrence of fetal distress in the diabetic group. The results suggest that fetal distress may be slightly more common in labour in diabetic women compared with controls managed in a similar way. Careful FHR monitoring and liberal use of fetal scalp blood pH determinations is recommended.

Meconium Aspiration and Fetal Acidosis

Meconium in labor is associated with increased perinatal morbidity and mortality. To identify the infants at risk, 53 women with moderate-to-thick meconium were followed in labor after obtaining baseline fetal scalp blood pH levels. Although 28 of the newborns (53%) exhibited an arterial cord pH of less than 7.25 at delivery, there were no significant predictive variables found in the electronic fetal monitoring score, Apgar score, or mode of delivery. Nine of the infants with a pH value of less than 7.25 had meconium below the vocal cords at delivery, but none in the infants with pH levels greater than or equal to 7.25. The P50 value for cumulative acidosis is 55 minutes, indicating a more rapid deterioration than an average-for-gestational-age fetus without meconium. Therefore, the presence of thick meconium implies that fetal stress must be avoided during labor, and early intervention is warranted when there is deviation from normal labor progress or fetal heart rate pattern.

Perinatal observations in a high-risk population managed without intrapartum fetal pH studies

Intrapartum fetal scalp blood pH studies remain controversial in obstetrics. Electronic fetal monitoring, by contrast, has achieved nearly uniform acceptance. Controlled comparative studies from one institution are unlikely to provide adequate numbers. Intrapartum fetal monitoring is used consistently at our institution. Fetal health is assessed by monitoring criteria, and intervention occurs only for obstetric or monitoring indications. With the presumption that intrapartum compromise and its management will usually be reflected in early neonatal findings, three recent years of perinatal results in a predominantly high-risk population of over 7100 deliveries are reported. Comparisons are made to results of other similar populations managed elsewhere with and without pH studies. Absence of pH studies did not appear to result in extraordinary rates of stillbirth, operative intervention, or neonatal compromise. The data are offered for interest but cannot by themselves prove the lack of worth of a test not used.

Simultaneous measurement of fetal tissue pH and transcutaneous pO 2 during labor

Simultaneous measurement of fetal heart rate (FHR), uterine contractions (UC), continuous fetal tissue pH (TpH) and transcutaneous pO 2 (tc pO 2) was attempted in 40 high-risk parturients monitored for an average duration of 117 ± 74 min. There were only two failures (9%) in the last 23 cases, with satisfactory recording of all parameters in 78% of the total. At present, the feasibility of simultaneous biochemical monitoring is limited to the active phase of labor. Fetal scalp and umbilical arterial blood pH and pO 2 were obtained as well. The biochemical data showed a good correlation between tc pO 2, scalp capillary pO 2 and umbilical artery pO 2 ( P < 0.02). The correlation was not significant between similar pH comparisons, although an average difference of 0.04 pH units was observed between the final TpH and umbilical artery pH. Both fetal TpH and tc pO 2 fell progressively during labor. Preliminary findings comparing TpH, tc pO 2 and FHR suggest that changes in tc pO 2 rapidly reflect changing maternal and fetal conditions, while TpH responds more slowly and less sensitively.

Fetal scalp blood lactate as an indicator of intrapartum hypoxia.

Fetal scalp blood lactate was measured during labour by a simple, rapid method and its value as an indicator of fetal intrauterine hypoxia was assessed and compared with that of pH measurement. The normal ranges of lactate concentration and of pH values were calculated. Significantly higher concentrations of lactate and lower pH values were found in samples of scalp blood taken close to delivery from babies with Apgar scores of less than or equal to 6 at 1 min compared with those from healthy babies with Apgar scores of greater than or equal to 7 at 1 min. A similarly significant difference was observed between the cord blood lactate and pH values of these two groups of babies. Ominous fetal heart rate patterns were associated with higher lactate concentrations and lower pH values in fetal scalp blood than were normal fetal heart rate patterns. The measurement of fetal scalp blood lactate or pH, or continuous electronic fetal heart rate monitoring were equally good at predicting the condition of the infant at birth.

Is End-Stage Deceleration of the Fetal Heart Ominous?

Little information is available on the significance of the dramatic fall in fetal heart rate which may occur during the second stage of labor. Although the drop appears ominous, the newborn infant is usually in excellent condition. In the present study, an attempt is made to assess the significance of end-stage deceleration and to discuss the management of labor in such cases. During the period from January 1 to July 1, 1980, 3540 women gave birth in the authors' medical center, and 1593 (45 per cent) had continuous fetal heart rate monitoring in labor. End-stage deceleration was diagnosed in 55 (3.4 per cent) of those monitored. The average drop in baseline fetal heart rate during end-stage deceleration was 45.5 beats per minute (range, 20 to 90 beats per minute). Forty-nine of the infants had one-minute Apgar scores of 7 or more; the remaining six were depressed at delivery and had one-minute Apgar scores of 5 or less. In 49 patients who had healthy babies, the fetal heart rate pattern preceding deceleration was normal. In the six patients who gave birth to depressed babies, pathological fetal heart rate patterns were present before deceleration, although fetal scalp blood pH in early labor was within normal limits. In four of these six, fetal scalp blood was sampled again during end-stage deceleration, and the pH was significantly lower. Vacuum extractor or outlet forceps were used in five deliveries; the sixth fetus was delivered spontaneously 5 minutes after the onset of deceleration, severely depressed and acidotic. Umbilical vein pH values in all six babies were acidotic. No relation was found between the depth of drop in fetal heart rate or the duration of deceleration and fetal condition on delivery, provided the heart rate was normal until end-stage deceleration. When umbilical vein pH values were related to the duration of deceleration, however, it was shown that values dropped to pre-acidotic levels when deceleration had persisted for more than 15 minutes (P < 0.001). The mean pH was 7.27 when end-stage deceleration lasted 1 5 minutes or less and 7.23 if deceleration persisted for more than 1 5 minutes (P < 0.001). Umbilical vein pH and the one-minute Apgar score were less dependent on the mode of delivery than on fetal heart rate patterns during labor and the duration of deceleration. Fetal scalp blood pH during end-stage deceleration was obtained from 25 patients and compared with umbilical vein blood pH. A weak correlation between the two could be demonstrated (r = 0.354), but all four infants who had low fetal scalp blood pH values during deceleration also had preacidotic or acidotic umbilical vein blood pH values.

Comparison of fetal scalp blood pH measurement with an automated blood microprocessor and a clinical blood gas laboratory

The Corometrics 220 pH System was compared to a clinical blood gas laboratory in the measurement of the pH of fetal scalp blood. The mean errors of measurement obtained in 49 samples was significantly less with the Corometrics 220 pH System than with the clinical blood gas laboratory. The 220 System was also more precise.

Fetal Heart Rate Patterns and Scalp Blood pH as Predictors of Fetal Distress

Division of Obstetrics and Gynecology, Soroka Medical Center, Faculty of Health Sciences. Ben-Gurion University of the Negev, Beersheba, Israel