Fetal Scalp Blood pH Research Articles

Fetal scalp blood sampling during second stage of labor – analyzing lactate or pH? A secondary analysis of a randomized controlled trial

Background Cardiotocography (CTG) is a widely used method for assessing fetal wellbeing during labor. It is well-known that CTG has high sensitivity but low specificity. To avoid unnecessary operative interventions, adjunctive methods such as fetal blood sampling (FBS) are used. Few studies have looked into whether FBS can be used during second stage of labor, and in that case, which of the methods (lactate or pH) are preferred. Objective To evaluate clinical effectiveness of measuring lactate versus pH in preventing birth acidemia when FBS was performed during second stage of labor. Methods Secondary analysis of a randomized controlled trial . Thousand three hundred and thirty-eight women with a singleton pregnancy, cephalic presentation, gestational age ≥34 weeks, and indication for FBS during second stage of labor were included. Main outcome measures Metabolic acidemia (pH <7.05 and base deficit >12 mmol/l) or pH < 7.00 in cord arterial blood at birth. Secondary outcomes A composite outcome (metabolic acidemia, pH <7 or Apgar score <4), and rates of operative deliveries. Results Metabolic acidemia occurred in 4.1% in the lactate versus 5.1% in the pH group (relative risk (RR): 0.80; 95% confidence interval (CI): 0.48–1.35) and pH <7 in 1.4% versus 2.8% (RR: 0.51, 95% CI: 0.23–1.13). Composite outcome was found in 3.8 versus 4.9%, respectively (RR: 0.76; 95% CI: 0.46–1.26). No difference in total operative interventions was found. More cesarean deliveries were performed in the lactate group (16.5 vs. 12.4%; RR: 1.33; 95% CI: 1.02–1.74). Conclusion When analyzing lactate or pH in fetal scalp blood during second stage of labor neonatal outcomes were comparable. The frequency of total operative interventions was similar but more cesarean deliveries were performed in the lactate group.

Infant outcome at four years of age after intrapartum sampling of scalp blood lactate for fetal assessment. A cohort study.

ObjectiveTo correlate the value of lactate in fetal scalp blood at delivery and the outcomes of the offspring at four years of age.MethodsCases where scalp blood lactate was taken within sixty minutes before delivery were identified from the randomized trial "Determination of pH or lactate in fetal scalp blood in management of intrapartum fetal distress”. Data were grouped according to the generally accepted cutoffs for normality, pre-acidemia, acidemia and concentrations above mean +2 SD during the second stage. The outcome measures included gross-/fine motor function, vision, hearing, speaking and cognitive disorders, signs of central motor damage and referral to specialized pediatric services.Results307 cases were available for final analyse. With normal scalp lactate concentration, the number of children with a diagnosed disorder was lower compared to the pre-acidemic/acidemic groups, although the findings were only significant for fine motor dysfunction (p = 0.036). Elevated lactate values were significantly associated with increased risk for a poorer capacity of attention and understanding of instructions (OR 1.37, 95% CI 1.07–1.74), and for fine motor dysfunction (OR 1.22, 95% CI 1.00–1.49) at the age of four.ConclusionHigher levels of lactate in fetal scalp blood seems to be associated with increased risk of an aberrant developmental outcome at four years of age in some areas.

Intérêt et faisabilité du Doppler cérébral en cours de travail pour prédire une acidose néonatale

ObjectivesTo evaluate feasibility and interest of fetal cerebral Doppler during labor and the link with fetal pH to predict perinatal fetal asphyxia. MethodsOur prospective study in a university perinatal center, included patients during labor. There were no risk factors during pregnancy and patients were included after 37 weeks of pregnancy. For each patient an ultrasound with cerebral Doppler was done concomitant to a fetal scalp blood sample. We collected maternal and fetal characteristics as well as cervix dilatation, fetal heart rate analysis and fetal presentation. ResultsAmong 49 patients included over a period of 4 months, cerebral Doppler failed in 7 cases (11%). Majority of failure occurred at 10cm of dilatation (P=0.007, OR=14.1 [1.483; 709.1275]). Others factors like: maternal age, body mass index, parity, history of C-Section were not associated with higher rate of failure. We did not found either significant correlation between cerebral fetal Doppler and pH on fetal scalp blood sample (r=0.15) nor pH at cord blood sample (r=0.13). No threshold of cerebral Doppler is significant for fetal asphyxia prediction. ConclusionFetal cerebral Doppler is feasible during labor with a low rate of failure but not a good exam to predict fetal acidosis and asphyxia.

Correlation of fetal scalp blood sampling pH with neonatal outcome umbilical artery pH value

Fetal scalp blood sampling is considered as a complimentary tool in addition to cardiotocography to assess fetal well-being. This blood sampling is important as the obstetrician has to judge and make decisions regarding the further management of the delivery based on this pH result. The aim of this study was to analyze the correlation between fetal scalp blood pH and the umbilical artery pH after birth. Furthermore, it was investigated whether tocolysis, a performed episiotomy or cord encirclement have an influence on the umbilical artery pH. This retrospective study over a period of 11years included all singleton pregnancies without fetal anomalies, which were monitored by fetal scalp blood sampling during labor. 844 out of 1502 deliveries were included for analysis. The analysis demonstrates a good correlation between fetal scalp pH value and outcome pH value. Subgroup analysis with fetal scalp blood pH<7.20 showed a difference in 40 of 82 cases, with an outcome pH value ≥7.20, but this difference was statistically insignificant. Neither did tocolysis, episiotomy or the presence of cord encirclement show an overall effect, nor did they have an impact on the subgroup. Obstetricians must consider that the values of fetal scalp blood are not always reliable and can be false. However, on the basis of CTG and fetal scalp blood pH, decisions are made regarding delivery interventions. Therefore, we would encourage the consideration of taking two samples routinely at every attempt of fetal blood sampling.

The value of fetal scalp blood lactate and/or pH analyses can only be evaluated in relation to neonatal outcome and not to frequency of interventions

The value of fetal scalp blood lactate and/or pH analyses can only be evaluated in relation to neonatal outcome and not to frequency of interventions

Scalp blood lactate for intra‐partum assessment of fetal metabolic acidosis

To study to what extent the fetal scalp blood lactate concentration during labor correlates with fetal scalp pH and base deficit, and metabolic acidosis at birth, and to suggest lactate cut-off values to serve as indicators for either reassurance or immediate intervention. A retrospective observational study. Labor ward at a university medical center. Fetal scalp and cord blood samples with acid-base and lactate values from 486 singleton pregnancies beyond 34 weeks' gestation. The relation between lactate, pH and base deficit (BD) in fetal scalp blood was tested by Spearman's rho correlation coefficient. Lactate cut-off values indicating either reassuring fetal status or immediate intervention were estimated using percentile distribution and compared with pH and BD. Metabolic acidosis, defined as umbilical cord artery pH below 7.05 and BD calculated for the blood compartment above 12 mmol/l. After 127 (21%) exclusions, 486 cases were available for analysis. Fetal lactate values increased with evolving metabolic acidosis. Lactate concentration correlated with both pH (r=-0.50, p<0.01) and BD (r=0.48, p<0.01). Lactate <5.4 mmol/l indicated reassuring fetal status, whereas lactate ≥6.6 mmol/l indicated metabolic acidosis. Fetal lactate correlated better with either the absence or presence of metabolic acidosis at birth than did fetal pH and BD. In the case of a non-reassuring fetal heart rate, fetal scalp blood lactate provides more accurate information on fetal acid-base status than does pH and/or BD.

Normalized spectral power of fetal heart rate variability is associated with fetal scalp blood pH

BackgroundSpectral power of fetal heart rate variability is related to fetal condition. Previous studies found an increased normalized low frequency power in case of severe fetal acidosis. AimsTo analyze whether absolute or normalized low or high frequency power of fetal heart rate variability is associated with fetal scalp blood pH. Study designProspective cohort study, performed in an obstetric unit of a tertiary care teaching hospital. SubjectsConsecutive singleton term fetuses in cephalic presentation that underwent one or more scalp blood samples, monitored during labour using ST-analysis of the fetal electrocardiogram. Ten-minute continuous beat-to-beat fetal heart rate segments, preceding the scalp blood measurement were used. Outcome measuresAbsolute and normalized spectral power in the low frequency band (0.04–0.15Hz) and in the high frequency band (0.4–1.5Hz). ResultsIn total 39 fetal blood samples from 30 patients were studied. We found that normalized low frequency and normalized high frequency power of fetal heart rate variability is associated with fetal scalp blood pH. The estimated ß of normalized low frequency power was −0.37 (95% confidence interval −0.68 to −0.06) and the relative risk was 0.69 (95% confidence interval 0.51–0.94). The estimated ß of normalized high frequency power was 0.33 (95% confidence interval 0.01–0.65) and the relative risk was 1.39 (95% confidence interval 1.01–1.92). ConclusionsNormalized low and normalized high frequency power of fetal heart rate variability is associated with fetal scalp blood pH.

Determination of pH or lactate in fetal scalp blood in management of intrapartum fetal distress: randomised controlled multicentre trial

Determination of pH or lactate in fetal scalp blood in management of intrapartum fetal distress: randomised controlled multicentre trial

Determination of pH or Lactate in Fetal Scalp Blood in Management of Intrapartum Fetal Distress: Randomized Controlled Multicenter Trial

Determination of pH or Lactate in Fetal Scalp Blood in Management of Intrapartum Fetal Distress: Randomized Controlled Multicenter Trial

Determination of pH or Lactate in Fetal Scalp Blood in Management of Intrapartum Fetal Distress: Randomized Controlled Multicenter Trial

Determination of pH or Lactate in Fetal Scalp Blood in Management of Intrapartum Fetal Distress: Randomized Controlled Multicenter Trial

Determination of pH or lactate in fetal scalp blood in management of intrapartum fetal distress: randomised controlled multicentre trial

Objective To examine the effectiveness of pH analysis of fetal scalp blood compared with lactate analysis in identifying hypoxia in labour to prevent acidaemia at birth.Design Randomised controlled multicentre trial.Setting...

Surveillance du travail dans les situations à risque

Intrapartum asphyxia is increased in several situations such as intrauterine growth retardation, preterm labor, postdate pregnancy or maternal diabetes. In all these cases, fetal heart rate monitoring should be preferred to intermittent auscultation. Fetal scalp blood pH or lactates can be used to identify fetuses at risk of intrapartum asphyxia. However, fetal scalp blood sampling should not delay delivery in case of severe abnormal fetal heart rate as fetal asphyxia could occur rapidly in theses high-risk pregnancies. Data is insufficient to recommend fetal pulse oximetry or ECG analysis. Research should be undertaken to evaluate their performance in these situations.

STAN® S21 fetal heart monitor for fetal surveillance during labor: an observational study in 637 patients

Objective: To assess the value of the STAN® fetal heart monitor for intrapartum fetal monitoring using cardiotocography (CTG) and fetal electrocardiography (ECG).Design: Prospective observational study.Material and methods: Between August 2000 and November 2002, 637 high-risk labors were monitored using a STAN® S21 fetal heart monitor, providing CTG plus automatic ST analysis of the fetal ECG. Guidelines with recommendations about when to intervene were available. During the study period labor-ward personnel were systematically instructed about the (patho)-physiology of asphyxia and CTG and ST changes during labor.Results: Four hundred and forty-nine recordings were available for analysis of outcome in relation to ST changes. In 61 cases, ST changes requiring intervention occurred > 10 min before birth. In 35 (57%) of these cases, umbilical artery blood pH at delivery was < 7.15. Eighteen (4.0%) neonates were born with metabolic acidosis (umbilical artery pH < 7.05 and extracellular base deficit > 12 mmol/l). Significant ST changes (18–31 min before birth) were present in all five cases with pH < 7.00 and in six of the 13 cases with pH of 7.00–7.04 (false-negative rate 1.6%). Neonatal follow-up showed no adverse outcome. One hundred and ninety-two fetal blood samples (121 in the first stage and 71 in the second stage of labor) were taken from 142 women. Fetal scalp blood pH was < 7.15 in ten samples, 7.15–7.19 in 11 samples, 7.20–7.24 in 30 samples and ⩾ 7.25 in 141 samples. ST changes occurred in eight (80%), six (55%), nine (30%) and 15 (11%) of these cases, respectively. In 188 (29.5%) women, outcome could not be analyzed in relation to ST changes because of inadequate recording (time between end of recording and delivery > 20 min or poor signal quality) or the absence of umbilical cord gases. In this group, four (2.1%) neonates with metabolic acidosis were born. In three of these cases the fetal ECG signal was of was poor quality and in one case the recording had ended 60 min before birth.Conclusion: ST changes were present in all five cases with severe metabolic acidosis (umbilical artery pH < 7.00). ST changes occurred in 46% of cases with mild metabolic acidosis. CTG plus ST analysis was more specific in detecting fetal acidemia than CTG alone.

Influence on fetal blood pH when adding amniotic fluid: an in vitro model.

To assess the effect of contamination with amniotic fluid in different quantities on fetal capillary blood pH. In vitro model. Department of Obstetrics, St Pölten Hospital. Venous umbilical blood and amniotic fluid from 35 women who underwent amniotomy during labour. Venous umbilical blood was mixed in vitro with amniotic fluid in diluted series (venous umbilical blood/amniotic fluid, 10:1 to 1:1). In every case two parallel runs of the dilution series in an inverted fashion were performed to rule out a possible time-dependent bias of the pH measurements. pH change in dilutions of umbilical venous blood with amniotic fluid: 10:1, +0.07 (0.02); 8:1, +0.08 (0.02); 6:1, +0.08 (0.03); 4:1, +0.07 (0.02); 2:1, +0.09 (0.03); 1:1, +0.12 (0.05); all P < 0.001. Amniotic fluid pH increases, whereas umbilical blood pH decreases slightly over time since collection. Dilutions of umbilical venous blood with amniotic fluid resulted in a significant pH rise. There was no significant difference between the two inversely performed dilution series. Amniotic fluid influences in vitro fetal venous blood pH immediately after contact. This observation indicates the possible masking of a fetus in distress by fetal scalp blood pH determination when amniotic fluid contaminates the sample.

Influence on fetal blood pH when adding amniotic fluid: an in vitro model

Objective To assess the effect of contamination with amniotic fluid in different quantities on fetal capillary blood pH. Design In vitro model. Setting Department of Obstetrics, St Pölten Hospital. Sample Venous umbilical blood and amniotic fluid from 35 women who underwent amniotomy during labour. Methods Venous umbilical blood was mixed in vitro with amniotic fluid in diluted series (venous umbilical blood/amniotic fluid, 10:1 to 1:1). In every case two parallel runs of the dilution series in an inverted fashion were performed to rule out a possible time-dependent bias of the pH measurements. Main outcome measures pH change in dilutions of umbilical venous blood with amniotic fluid: 10:1, +0.07 (0.02); 8:1, +0.08 (0.02); 6:1, +0.08 (0.03); 4:1, +0.07 (0.02); 2:1, +0.09 (0.03); 1:1, +0.12 (0.05); all P < 0.001. Results Amniotic fluid pH increases, whereas umbilical blood pH decreases slightly over time since collection. Dilutions of umbilical venous blood with amniotic fluid resulted in a significant pH rise. There was no significant difference between the two inversely performed dilution series. Conclusion Amniotic fluid influences in vitro fetal venous blood pH immediately after contact. This observation indicates the possible masking of a fetus in distress by fetal scalp blood pH determination when amniotic fluid contaminates the sample.

Predictive value of pulse oximetry and fetal scalp blood pH in the case of meconium-stained amniotic fluid

Objective: To compare the predictive value of intrapartum fetal pulse oximetry to that of fetal scalp blood pH for an abnormal neonatal outcome in the case of thick meconium. Study design: A prospective multicenter observational study was performed from June 1994 to November 1995. Fetal oxygen saturation was monitored using a Nellcor N-400 fetal pulse oximeter in case of abnormal FHR. The last readings of fetal oxygen saturation and fetal scalp blood pH before birth were used to assess the ability of both techniques to predict an abnormal neonatal status. Results: At a 30% cutoff, the negative predictive value of fetal oxygen saturation was not altered in case of meconium when compared to clear amniotic fluid (79 and 83%, respectively). Fetal scalp blood pH at a 7.20 threshold had a poor negative predictive value in case of meconium when compared to clear amniotic fluid (56% versus 88%, respectively). The receiver operator characteristic curve showed similar performance of fetal scalp blood pH and pulse oximetry in cases with clear amniotic fluid. In cases with meconium, the performance of fetal scalp blood pH was poor, whereas that of pulse oximetry remained unchanged. In three cases with meconium below the vocal cords, a drop in fetal oxygen saturation was observed during labor whereas fetal scalp blood pH remained within normal values. Conclusion: The predictive value of fetal scalp blood pH is poor in case of meconium, whereas the predictive value of pulse oximetry seems to be unchanged in this situation.

Is intrapartum vibroacoustic stimulation an effective predictor of fetal acidosis?

The hypothesis of this prospective study is that intrapartum vibroacoustic stimulation (VAS) is an effective predictor of fetal acidosis during labor. Various clinical conditions, such as term versus preterm gestation, first stage versus second stage of labor, and fetal heart rate (FHR) variable decelerations versus late decelerations will be tested. During the study period, 113 patients were studied prospectively in either active phase of first stage (n = 53) or during the second stage of labor (n = 60). They were selected from cases exhibiting moderate to severe FHR variable decelerations or late decelerations. The fetuses of study subjects received a VAS for three seconds and FHR changes were recorded. Fetal scalp blood pH or umbilical arterial blood pH was obtained within 15 minutes of VAS. The relationship between FHR responses to VAS and fetal blood pH in term and preterm gestations, the relationship of two tests (VAS and fetal blood pH) to type of FHR decelerations, and the predictability of neonatal morbidity by two tests were analyzed. Where appropriate, Fisher's exact test (p < 0.05 was considered statistically different) and the odd ratio with 95% confidence intervals were used for statistical analyses. Excellent association between acceleration response to VAS and pH > or = 7.20, and between a negative response to VAS (no acceleration or decelerations) and pH < 7.20 were found in the first stage of labor, the second stage of labor, and the combination of both stages together (p = 0.0001, OR = 10.6 [3.3-34.0]). It was observed that negative VAS responses for predicting fetal acidosis (pH < 7.20) were comparable between term (> or = 37 weeks) and preterm (< 37 weeks, > or = 34 weeks) fetuses. Since the preterm fetuses enrolled in the study were limited in number, it is difficult to draw adequate conclusions. The positive predictive value (PPV) of fetal acidosis was 67% in both groups of FHR variable decelerations and late decelerations, but the false negative rate of acceleration VAS response for predicting no acidosis was significantly higher in the group of late decelerations (29% vs 8%, p = 0.034). Finally, both a negative VAS response and fetal acidosis (pH < 7.20) have equal predictability for neonatal morbidity. The PPV of NICU admission by a negative VAS response was two times higher than that of fetal acidosis (PPV = 61% vs 29%, p = 0.038). We found that intrapartum VAS was an effective predictor of fetal acidosis in cases of FHR variable decelerations, but its predictability for fetal acidosis in cases of FHR late decelerations was limited. Both VAS and fetal blood pH are good predictors of neonatal morbidity.

Measuring fetal scalp blood lactate during labour

Fetal blood lactate can easily and safely be measured with the new microvolume lactate meter. The system requires only 5µl of blood and gives the result in 60 seconds. As opposed to pH meters, the lactometer is considerably cheaper and does not require trained staff or regular attention from a technician. Trials have shown the levels of lactate and pH in fetal scalp blood to be comparable in predicting low Apgar scores at delivery as well as the need for neonatal intensive care unit admission. Lactate concentration in umbilical artery blood has also been shown to have the same predictive properties as pH in relation to perinatal morbidity and mortality. Owing to its simplicity of performance, lactate analysis with the new test strip method is an attractive complement of intrapartum fetal monitoring.

Predictive value of fetal scalp blood lactate concentration and pH as markers of neurologic disability

Objectives: We aimed to analyze the predictive value of the fetal scalp blood lactate concentration and pH, especially in regard to outcome variables that are strong predictors of impaired long-term outcome. An additional aim was to establish cutoff lactate levels in fetal scalp blood. Study Design: We conducted a retrospective study of all patients who had fetal scalp blood sampling performed because of an ominous fetal heart rate pattern at Huddinge University Hospital from October 1993 to October 1998. Fetal scalp blood sampling was performed in 1709 patients. The pH and the lactate concentration were determined in fetal scalp blood of 1221 and 814 of these patients, respectively. Outcome variables included pH <7.0 in umbilical artery blood; base deficit >16.0 mmol/L in umbilical artery blood; Apgar scores <7 at 1 minute, <7 at 5 minutes, and <4 at 5 minutes; and hypoxic-ischemic encephalopathy. Results: Sensitivity and specificity were generally higher in the lactate group than in the pH group, particularly in relation to an Apgar score <4 at 5 minutes and moderate to severe hypoxic-ischemic encephalopathy. In 326 patients the scalp blood lactate concentration and pH value had been obtained at the same time, thus allowing a comparison between these methods. The areas under the receiver operating characteristic curves were significantly higher for the lactate concentration than for the pH value with 2 outcome variables: Apgar score <4 at 5 minutes ( P = .033) and moderate to severe hypoxic-ischemic encephalopathy ( P = .015). Conclusions: Our findings suggest that determination of the lactate concentration in fetal scalp blood is a more sensitive diagnostic tool than is determination of the pH value for predicting either an Apgar score <4 at 5 minutes or moderate to severe hypoxic-ischemic encephalopathy. In previous studies we also showed lactate measurements to be more often successful than pH analysis. Therefore we consider the measurement of lactate in fetal scalp blood to be an attractive alternative to pH analysis, and determination of the lactate concentration in fetal scalp blood seems to be a useful tool for monitoring the condition of the fetus. A suitable cutoff limit for fetal scalp blood lactate concentration as an indicator of fetal asphyxia could be 4.8 mmol/L. (Am J Obstet Gynecol 1999;181:1072-8.)

Requiem for a heavyweight: the demise of scalp blood pH sampling.

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."