Newborn complications after intrapartum asphyxia with metabolic acidosis in the term fetus

Systemic and cerebral inflammatory response to umbilical cord occlusions with worsening acidosis in the ovine fetus

OBJECTIVE

We hypothesized that repetitive umbilical cord occlusions (UCOs) with worsening acidosis will lead to a fetal inflammatory response.

STUDY DESIGN

Chronically instrumented fetal sheep underwent a series of UCOs until fetal arterial pH decreased to <7.00. Maternal and fetal blood samples were taken for blood gases/pH and plasma interleukin (IL)-1B and IL-6 levels. Animals were euthanized at 24 hours of recovery with brain tissue processed for subsequent measurement of microglia and mast cell counts.

RESULTS

Repetitive UCOs resulted in a severe degree of fetal acidemia. Fetal plasma IL-1B values were increased approximately 2-fold when measured at maximal fetal acidosis and again at 1-2 hours of recovery. Fetal microglia cells were increased approximately 2-fold in the white matter and hippocampus, while mast cells were increased approximately 2-fold in the choroid plexus and now evident in the thalamus when analyzed at 24 hours recovery.

CONCLUSION

Repetitive UCOs leading to severe acidemia in the ovine fetus near term will result in an inflammatory response both systemically and locally within the brain.

INTRAPARTUM ST ANALYSIS

The last century has seen dramatic developments in medical care as technological advances have been applied to both diagnosis and treatment. Some areas of obstetrics have been slow to benefit from these advances – and none more so than the care of the fetus in labour.

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

Labour wards.

PARTICIPANTS

Women with a singleton pregnancy, cephalic presentation, gestational age >or=34 weeks, and clinical indication for fetal scalp blood sampling.

INTERVENTIONS

Standard pH analysis (n=1496) or lactate analysis (n=1496) with an electrochemical microvolume (5 mul) test strip device. The cut-off levels for intervention were pH <7.21 and lactate >4.8 mmol/l, respectively.

MAIN OUTCOME MEASURE

Metabolic acidaemia (pH <7.05 and base deficit >12 mmol/l) or pH <7.00 in cord artery blood.

RESULTS

Metabolic acidaemia occurred in 3.2% in the lactate group and in 3.6% in the pH group (relative risk 0.91, 95% confidence interval 0.61 to 1.36). pH <7.00 occurred in 1.5% in the lactate group and in 1.8% in the pH group (0.84, 0.47 to 1.50). There was no significant difference in Apgar scores <7 at 5 minutes (1.15, 0.76 to 1.75) or operative deliveries for fetal distress (1.02, 0.93 to 1.11).

CONCLUSION

There were no significant differences in rate of acidaemia at birth after use of lactate analysis or pH analysis of fetal scalp blood samples to determine hypoxia during labour.

TRIAL REGISTRATION

ISRCT No 1606064.

Umbilical cord blood lactate: a valuable tool in the assessment of fetal metabolic acidosis

OBJECTIVE

The aim of the present study was (1) to evaluate the relationship between umbilical cord arterial blood lactate and pH, standard base excess (SBE), and actual base excess (ABE) at delivery and (2) to suggest a cut-off level of umbilical cord arterial blood lactate in predicting fetal asphyxia using ROC-curves, where an ABE value less than -12 was used as "gold standard" for significant intrapartum asphyxia.

STUDY DESIGN

This is a descriptive study of umbilical cord arterial blood samples from 2554 singleton deliveries. The deliveries took place at the Department of Obstetrics and Gynaecology, Hvidovre University Hospital, Copenhagen, Denmark where umbilical cord blood sampling and blood gas analysis is part of the routine assessment of all newborns.

RESULTS

We found significant correlations between lactate and pH (r=-0.73), lactate and SBE (r=-0.76), and lactate and ABE (r=-0.83). ROC-curves suggested a lactate cut-off level of 8mmol/l for indicating intrapartum asphyxia.

CONCLUSION

Lactate in arterial umbilical cord blood might be a more direct and accordingly more correct indicator of fetal asphyxia at delivery than pH and SBE (or ABE). Its potential as a predictor of neonatal outcome needs to be evaluated in future studies.

Use of umbilical cord blood gas analysis in the assessment of the newborn

Analysis of paired arterial and venous specimens can give insights into the aetiology of acidosis in the newborn

Fetal cerebral oxygenation: the role of maternal hyperoxia with supplemental CO2 in sheep

OBJECTIVE

We tested the hypothesis that supplemental CO2 can enhance the effect of maternal oxygen administration on fetal cerebral oxygenation.

STUDY DESIGN

In near-term fetal sheep (n = 6), we instrumented the cerebral cortex with tissue PO2-laser Doppler flow probes, and placed arterial catheters. Following a 30-minute control period, the ewe breathed 50% O2 for 15 minutes, followed by added 6% CO2 for 15 minutes. We examined fetal cortical tissue PO2, cerebral blood flow (CBF), and fetal and maternal blood gases and related variables.

RESULTS

In response to maternal O2 administration, fetal arterial PO2, O2 content, cerebral O2 delivery, and cortical tissue PO2 increased significantly. In response to supplemental CO2 inhalation, fetal cortical tissue PO2 increased further. Fetal CBF also increased in response to the elevated arterial CO2 level.

CONCLUSION

CO2 supplementation of maternal O2 administration enhanced fetal cerebral oxygenation. In contrast, it was considered that during labor maternal hyperventilation with hypocapnia may blunt the effect of maternal O2 inhalation.

Fetal hypercapnia and cerebral tissue oxygenation: studies in near-term sheep

The precise role of CO2 in cerebral oxygenation is not as well defined as O2, especially in the immature brain. In the ovine fetus, we tested the hypotheses that arterial Pco2 (Paco2) plays a critical role not only in the regulation of cerebral blood flow but also in the regulation of cerebral tissue oxygenation. By use of a fluorescent O2 probe with a laser Doppler flowmeter and the placement of sagittal sinus catheter in six near-term fetal sheep, we measured values of cortical tissue O2 tension (tPo2), sagittal sinus oxyhemoglobin saturation ([HbO2]), and laser Doppler cerebral blood flow (LD-CBF) in response to 20 min hypercapnia induced by having the ewe breathe CO2. In response to moderate to severe hypercapnia, LD-CBF increased above baseline in a curvilinear fashion, cortical tPo2 increased linearly (1 torr per 3.2 torr Paco2), and sagittal sinus [HbO2] increased significantly in a curvilinear manner. Hypercapnia favored cerebral tissue oxygenation of the fetal brain; and cortical tPo2 and sagittal sinus [HbO2] complement or support one another as indices of cerebral oxygenation under hypercapnic conditions.

Base deficit estimation in umbilical cord blood is influenced by gestational age, choice of fetal fluid compartment, and algorithm for calculation

OBJECTIVE

The purpose of this study was to explore the influences of gestational age, the choice of fetal fluid compartment, and the algorithm for calculation on the estimation of the base deficit in umbilical cord arterial blood at birth.

STUDY DESIGN

From 1995 to 2002, cord arterial blood gases and obstetric data were available for 43,551 newborn infants at 37+ weeks of gestation (cohort I). The mean base deficit in blood and the base deficit in extracellular fluid were estimated from pH and PCO2 values in 28,213 newborn infants with a 5-minute Apgar score of > or = 9 (cohort II) with the use of 3 different calculation algorithms (base deficit in blood, base deficit in extracellular fluid [A], and base deficit in extracellular fluid [B]).

RESULTS

In cohort II, the base deficit in blood, the base deficit in extracellular fluid (A), and the base deficit in extracellular fluid (B) increased with advancing gestational age (linear regression; P < .0001). The curves run almost parallel, with the base deficit in blood being higher than the base deficit in extracellular fluid (A) and (B). With the use of receiver operating characteristic curves in cohort I, the area under curve to indicate a 5-minute Apgar score of < 7 and < 4 showed the area under curve-pH to be greater than the area under curve-base deficit in extracellular fluid (A) and (B), the area under curve-base deficit in blood to be greater than the area under curve-base deficit in extracellular fluid (A) and (B) for a 5-minute Apgar score of < 7, and the area under curve-base deficit in blood to be greater than the area under curve-base deficit in extracellular fluid (A) and (B) for an Apgar score of < 4. The cutoffs with highest sensitivity and lowest false-positive rate for a 5-minute Apgar score of < 7 and < 4 were, for both scores, a pH value of 7.15, a base deficit in blood of 10 mmol/L, a base deficit in extracellular fluid (A) of 8 mmol/L, and a base deficit in extracellular fluid (B) of 6 mmol/L.

CONCLUSION

The calculated values of the base deficit in umbilical cord arterial blood are influenced decisively by gestational age, the choice of fetal fluid compartment, and the calculation algorithms that are used. The power of the base deficit to indicate neonatal distress depends on the choices of fluid compartment and the algorithm that is used to calculate the base deficit.

Acid–base balance of umbilical artery blood of liveborn piglets at birth and its relation with factors affecting delivery of individual piglets

In the limited number of studies that reported on the relation between factors affecting birth of individual piglets and acid-base balance values at birth, predominantly simple correlation coefficients have been used. The aim of the present study was to analyse the relation between factors affecting delivery of individual liveborn piglets and acid-base balance values (pH, PCO(2) , HCO(3)(-) and BE(ecf)) at birth. In total 201 piglets originating from 44 litters were used for the collection of blood samples from the umbilical artery immediately after birth, preferably in the period of apnea. Blood samples were analysed with the iStat Portable Clinical Analyser. Significantly lower pH, HCO(3)(-), BE(ecf) and significantly higher PCO(2) levels were found in posteriorly presented piglets, independently of the condition of the umbilical cord, birth weight and cumulative birth interval/rank. Independently of presentation, birth weight and rank, piglets born with ruptured umbilical cords showed significantly lower pH values. Next to that, increasing birth weights resulted in increasing HCO(3)(-) and BE(ecf) values at birth, independently of presentation, condition of the umbilical cord and cumulative birth interval/rank. Both an increase in cumulative birth interval and in rank was associated with a significant decrease of pH, HCO(3)(-), BE(ecf) and increase of PCO(2) levels in umbilical cord blood at birth. Together these results demonstrate for the first time that a clear relation exists between (factors affecting) the progress of delivery and acid-base balance values in a polytocous species like the pig.

Fetal pulse oximetry and wavelet analysis of the fetal heart rate in the evaluation of abnormal cardiotocography tracings

AIM

Previous studies indicate that the addition of wavelet analysis of the fetal pulse oximetry tracings (FSPO2) and fetal heart rate (FHR) variability to cardiotocography (CTG), for intrapartum fetal monitoring, provides useful information on the fetal response to hypoxia. We applied the new procedure in non-reassuring CTG patterns, in which cesarean section was performed, and tested its accuracy in the diagnosis of the intrapartum fetal compromise.

METHODS

At the 'Aretaieion' University Hospital labor ward, 318 women with term fetuses in the cephalic presentation entered the trial during labor. They all were monitored with external CTG and fetal pulse oximetry. In the cases that cesarean section was applied, because of abnormal CTG tracings, we applied a method based on the multiresolution wavelet analysis and a self-organized map neural network on the first and second stage of labor. The main outcome parameter was the rate of cord metabolic acidosis at birth (pH < 7.05). Secondary outcomes included Apgar scores at 5 min, fetal transmission to neonatal intensive care unit (NICU) and neonatal encephalopathy.

RESULTS

Fifty out of 318 cases delivered operatively because of abnormal CTG patterns (rate 15.72%). In 30 cases, cord pH was >7.05, while in 11 Apgar scores at 5 min were <7, while none of those neonates were transferred to NICU. In the rest 20 cases cord pH was <7.05; in all of these cases Apgar scores at 5 min were <7, while four neonates were transferred to NICU. In one of them, neonatal encephalopathy was diagnosed. After the offline application of wavelet analysis and neural networks to the pulse oximetry and FHR variability readings of the 50 cases, statistics calculated that the system showed a sensitivity of 85% and a specificity of 93%, while false negative and false positive rates were 15% and 7%, respectively.

CONCLUSION

Computerized FHR and FSPO2 monitoring shows an excellent efficacy and reliability in interpreting non-reassuring FHR recordings.

Intrauterine asphyxia: clinical implications for providers of intrapartum care

Advances in science and technology have allowed researchers to gain a better understanding of the pathophysiology leading to long-term neurologic damage in newborns. Intrapartum events are now known to be an infrequent cause of adverse neurologic outcome. Clinicians caring for women during labor must have an understanding of the pathophysiology of intrauterine asphyxia as well as an awareness of the capabilities and limitations of available intrapartum fetal assessment tools to diagnose intrauterine fetal asphyxia or predict neurologic outcome. This article reviews the physiology of acid-base balance and fetal gas exchange as well as the current scientific understanding of the role of intrauterine asphyxia in the pathophysiology of neonatal encephalopathy and cerebral palsy. Recommendations for care and documentation are included.

Metabolomic and bioinformatic analyses in asphyxiated neonates

OBJECTIVES

We tested the application of bioinformatic algorithms in studying the metabolomic profiles of neonatal urine samples with clinical evidence of severe asphyxia at birth and subsequent neurodevelopmental handicap.

DESIGN AND METHODS

The clinical outcomes of 256 newborns that required direct admission to neonatal intensive care unit for respiratory support or did not require direct admission were studied. Urinary metabolite profiles were measured by high throughput mass spectrometry and analyzed by bioinformatic methods.

RESULTS

We found a positive relationship between suppressed biochemical networks involved in macromolecular synthesis and birth asphyxia associated with significant neonatal oxidative stress and morbidity. The metabolomic discriminators between good neonatal outcome and poor neonatal outcome were established using hierarchical clustering analysis. Concentrations of eight urinary organic acids in distinct biochemical pathways were elevated and significantly associated with the prognosis of neurodevelopmental handicap with high sensitivity and specificity: ethylmalonate, 3-hydroxy-3-methylglutarate, 2-hydroxy-glutarate and 2-oxo-glutarate were associated with good neonatal outcome, whereas glutarate, methylmalonate, 3-hydroxy-butyrate and orotate were associated with poor outcome.

CONCLUSIONS

The data demonstrated the potential application of bioinformatics methods in this metabolomic study and proved its clinical relevance.

Umbilical artery Doppler and umbilical cord pH at birth in small-for-gestational-age fetuses: valid estimate of their relationship

OBJECTIVE

To evaluate the relationship between umbilical artery pulsatility index and the umbilical cord pH in small-for-gestational-age fetuses.

METHODS

Data were collected from all pregnancies seen in our Fetal Surveillance Unit that underwent antenatal monitoring for being small-for-gestational-age beyond 24 weeks of pregnancy. A linear regression was used to analyse the effect of the umbilical artery pulsatility index (UAPI) and umbilical artery pH at birth, assessing interaction and controlling for clinically meaningful antenatal, Doppler, biophysical and perinatal variables.

RESULTS

A total of 117 pregnancies were included. According to the estimated model (which included all clinically significant confounders and statistically significant interactions), in cases with reactive cardiotography (CTG) a 1-unit increase in the UAPI resulted in a mean decrease of 0.021 (95% 0.05 to -0.005) units of umbilical artery pH at delivery. In the non-reactive CTG group a 1-unit increase in the UAPI resulted in a mean decrease of 0.02 (95% CI 0.059 to -0.019) units of umbilical artery pH at delivery. Finally, in fetuses with a pathological CTG a 1-unit increase in the UAPI resulted in a mean decrease of 0.149 (95% CI 0.107 to 0.19) units of umbilical artery pH at delivery.

CONCLUSIONS

The crude effect between umbilical artery velocimetry on umbilical artery pH at birth has to be interpreted with caution, since an important part of this effect is related to other factors that confound and modify the relationship. After controlling for confounders, it was only in fetuses with pathological CTG that the effect remained statistically significant.

Computerized cardiotocography in the management of intrauterine growth restriction associated with Doppler velocimetry alterations

OBJECTIVE

To verify the reliability of computerized cardiotocography (cCTG) in the prediction of the oxygen metabolism status of fetuses with growth restriction and Doppler velocimetry alterations.

METHODS

From 24 third-trimester cesarean section performed because of intrauterine growth restriction (IUGR) and Doppler velocimetry alterations, there were 11 cases of fetal heart rate alterations (Dawes-Redman criteria were not satisfied) and 13 cases of reactive cCTG. Fetal lung maturity was detected by amniocentesis and blood samples for umbilical blood gas analysis (UBGA) were collected before the first neonatal breath from the umbilical artery in a double-clamped segment of the cord.

RESULTS

Umbilical cord gas analysis showed arterial cord blood pH to be 7.20 or less in 11 newborns (45.8%), 7.10 or less in 6 (25%), and 7.00 or less in 3 (12.5%). Linear regression analysis showed short-term variation (STV) in the fetal heart rate to be significantly correlated with umbilical artery pH (r = 0.49; P = 0.01) and pCO2 (r = -0.50; P = 0.01). There were no significant correlations between cCTG and the other UBGA parameters considered. Receiver operator curves permitted to calculate the STV values at which pathological neonatal UBGA values can be expected (pH < 7.00 and pCO2 > 80 mmHg). A short-term variation less than 4.5 ms was found to predict acidemia with a sensitivity of 100% and a specificity of 70% (positive predictive value, 33%; negative predictive value, 100%), and hypercarbia with a sensitivity of 100% and a specificity of 77.8% (positive predictive value, 55.6%; negative predictive value, 100%).

CONCLUSION

In view of the results of this study, 4.5 ms for STV may be a threshold below which timing of delivery should be decided in cases of fetal growth restriction.

Acid-base status at birth, spontaneous motor behaviour at term and 3 months and neurodevelopmental outcome at age 4 years in full-term infants

OBJECTIVE

The aim of the study was to assess the relationship between acid-base status and quality and quantity of General Movements (GMs) at birth and quality of GMs at age 3 months and motor, cognitive and behavioural functioning at the age of 4 years.

METHODS

From a cohort of 84 term children with different umbilical artery pH without severe neonatal neurological abnormalities, GMs were assessed at term and at 3 months. At the age of 4 years, 44 children were assessed by means of the Movement Assessment Battery for Children (Movement-ABC), Neurological Examination for Toddlers of Hempel, Kaufman Assessment Battery for Children information processing (Kaufman ABC), Visuomotor Integration (VMI), the Child Behaviour Checklist (CBCL) and Precursors ADHD Questionnaire (PAQ).

RESULTS

We found no relationship between pH or GM-quality and quantity at term or GM-quality at 3 months and scores on most of the items of the Movement-ABC, cognitive and behavioural outcome. However, neonatal pH value and GM-quality at 3 months were related to some extent to the presence of subtle signs of neuromotor dysfunction as measured by the Hempel test.

CONCLUSIONS

In a sample of infants with a large variation in umbilical artery pH and without severe neonatal neurological abnormalities, acid-base status at birth and quality of GMs at 3 months of age is not predictive for motor milestone achievement, cognitive and behavioural functioning at 4 years, but these parameters are related to a less optimal condition of the nervous system. The latter finding has, however, limited clinical significance.

Combination of early perinatal factors to identify near-term and term neonates for neuroprotection

OBJECTIVE

To determine early predictors of abnormal outcome at > or =24 months' age in neonates at risk for hypoxic-ischemic brain injury.

STUDY DESIGN

A prospective cohort study with developmental follow-up of > or =24 months. Infants were selected based on risk factors, and neurologic outcome was determined. Variables affecting the outcome were evaluated with univariate and multivariate methods, and a scoring system was devised to predict adverse outcome.

RESULTS

A total of 41 infants born > or =35 weeks' gestational age with possibility of hypoxic-ischemic insult were enrolled. In all, 39 (95%) had known outcomes, of whom 17 (48%) had an abnormal neurologic outcome, including five deaths. The variables within the first hour of life correlating with the adverse outcome were 1- and 5-minute Apgar scores, intubation in the delivery room and cord/initial base-deficit > or =20 mmol/l. A scoring system was derived based on significant variables, and a score > or =5 had a 90% positive predictive value for abnormal outcome. Seizures, multiorgan failure and abnormal imaging studies were also significantly associated with abnormal outcome.

CONCLUSIONS

The proposed scoring system, being highly predictive of outcome at 24 months' age, may be potentially useful in selecting subjects for preventive or therapeutic interventions to prevent or minimize neurologic morbidity due to hypoxic brain injury.

Computerized cardiotocography parameters in pregnant women affected by pregestational diabetes mellitus

AIM

To evaluate whether computerized CTG (cCTG) is a reliable method of predicting neonatal outcome in pregnancies complicated by pregestational diabetes at term.

PATIENTS AND METHODS

We considered 27 pregnant women affected by pregestational diabetes and 46 normal pregnancies as controls that fulfilled the following criteria: singleton, Caucasian, euglycemic pregnancies at term (>37 weeks gestational age). All women delivered by cesarean section (CS), with an antepartum cCTG performed within one hour before the CS and an UBGA available at birth. No patient was in labor during FHR monitoring.

RESULTS

Among cCTG parameters, accelerations 15 bpm, HV min, HV ms and STV were significantly lower in comparison to controls. We observed that in the diabetic pregnant women the parameter STV was not able to predict or to linearly regress with the most important UBGA parameters: pH and pCO2. Contrarily, in normal pregnancies, the STV linearly regressed with both the pH (p < 0.03) and pCO2 (p<0.04).

CONCLUSIONS

Computerized FHR criteria may not be applicable to fetuses in pregestational diabetic pregnancies at term. Therefore some criteria should perhaps be modified for a correct interpretation of cCTG in these pregnancies.

Umbilical cord pH and base excess values in relation to adverse outcome events for infants delivering at term

OBJECTIVE

This study was undertaken to determine the relationship of umbilical cord pH and base excess (BE) values to adverse neonatal outcomes for a large tertiary hospital population delivering at term. Study design The perinatal/neonatal database of St. Joseph's Health Care, London, Canada, was used to obtain the umbilical cord pH and BE values, incidence of adverse neonatal outcomes, and patient demographics for all term (>/=37 weeks' gestation), singleton, liveborn infants with no major anomalies delivering between November 1995 and March 2002 (n=20,456). Statistical analyses included chi(2) analysis, logistic regression models to develop odds ratios and creation of receiver operating characteristic (ROC) curves with area under curve (AUC) calculations.

RESULTS

Umbilical vein and artery pH and BE values for this tertiary care population averaged 7.33 +/- 0.06 and 7.24 +/- 0.07, and -4.5 +/- 2.4 and -5.6 +/- 3.0 mmol/L, respectively. Apgar less than 7 at 5 minutes, neonatal intensive care unit (NICU) admission, and assisted neonatal ventilation had significant inverse relationships with both umbilical artery and umbilical vein pH and BE (all P < .0001), with marginal increases in the incidences of these outcomes beginning with cord blood values close to the mean, and more substantial increases with cord values less than 1 or 2 SD below the mean, depending on the outcome studied. The ROC AUC for all these relationships were significant (P < .001) ranging from 0.76 to 0.79 when predicting Apgar less than 7 at 5 minutes to 0.68 to 0.70 when predicting NICU admission, and with cutoff cord blood values at which sensitivity and specificity were maximized again close to mean values. For each of these neonatal outcomes, the relation to cord blood values was similar with little difference in the data analysis whether using pH or BE values, and whether from the umbilical artery or vein.

CONCLUSION

There is a progression of risk in term infants for Apgar less than 7 at 5 minutes, NICU admission, and need for assisted ventilation with worsening acidosis at birth, which begins with cord blood values close to mean values indicating a higher threshold for associated acidemia with these outcomes than is seen for more severe neonatal outcomes.

Determining the contribution of asphyxia to brain damage in the neonate

Studies in the research laboratory have demonstrated the complex relationship between fetal and newborn asphyxia and brain damage, a balance between the degree, duration and nature of the asphyxia and the quality of the cardiovascular compensatory response. Clinical studies would support the contention that the human fetus and newborn behave in a similar manner. An accurate diagnosis of asphyxia requires a blood gas and acid base assessment. The clinical classification of fetal asphyxia is based on a measure of metabolic acidosis to confirm that fetal asphyxia has occurred and the expression of neonatal encephalopathy and other organ system complications to express the severity of the asphyxia. The prevalence of fetal asphyxia at delivery is at term, 25 per 1000 live births of whom 15% are moderate or severe; and in the preterm, 73 per 1000 live births of whom 50% are moderate or severe. It remains to be determined how often the asphyxia recognized at delivery may have been present before the onset of labor. There is a growing body of indirect and direct evidence to support the contention that antepartum fetal asphyxia is important in the occurrence of brain damage. Although much of the brain damage observed in the newborn reflects events that occurred before delivery, newborn asphyxia and hypotension, particularly in the preterm newborn, may contribute to the brain damage accounting for deficits in surviving children.

Fetal scalp and cord blood lactate

Lactate measurements have been evaluated in intrapartum fetal surveillance for some 30 years. However, it was not until reliable, handheld, microvolume devices were launched during the 1990s that lactate became a clinical option. Retrospective data suggest that lactate determinations in fetal scalp blood are better than pH for predicting severe neonatal morbidity. A randomised controlled trial comparing these two measurements found lactate to be more favourable in clinical practice in terms of less sampling failure and reduced time from the decision to do a fetal scalp blood sample to the clinician receiving the result. At present, a large multicenter randomised control trial is in progress in Sweden to compare lactate and pH measurement for the clinical management of suspected fetal compromise. Main end-points in the study are metabolic acidemia or pH <7.00 in cord arterial blood at delivery. Results are likely to be available in 2-3 years time.

Reflections on the occurrence and significance of antepartum fetal asphyxia

This chapter documents the growing evidence of the occurrence and significance of antepartum fetal asphyxia. Perinatal mortality studies demonstrate that the majority of fetal deaths, including those due to asphyxia, occur in the antepartum period. Epidemiological studies of cerebral palsy conclude that a minority of cases of cerebral palsy are due to intrapartum fetal asphyxia and implicate antenatal events, including asphyxia. Cordocentesis studies have confirmed that antepartum fetal asphyxia occurs in the growth-restricted fetus and might contribute to the increase of stillbirths and cerebral palsy in these children. Blood gas and acid-base studies in the immature fetus have demonstrated the increased prevalence of fetal asphyxia, and particularly of moderate or severe asphyxia, of which the majority might occur in the antepartum period. The ultimate determination of the prevalence and significance of antepartum fetal asphyxia requires the development of a non-invasive specific measure of fetal asphyxia.

Postnatal lactate as an early predictor of short-term outcome after intrapartum asphyxia

OBJECTIVES

To compare the predictive value of pH, base deficit and lactate for the occurrence of moderate-to-severe hypoxic ischaemic encephalopathy (HIE) and systemic complications of asphyxia in term infants with intrapartum asphyxia.

STUDY DESIGN

We retrospectively reviewed the records of 61 full-term neonates (> or =37 weeks gestation) suspected of having suffered from a significant degree of intrapartum asphyxia from a period of January 1997 to December 2001. The clinical signs of HIE, if any, were categorized using Sarnat and Sarnat classification as mild (stage 1), moderate (stage 2) or severe (stage 3). Base deficit, pH and plasma lactate levels were measured from indwelling arterial catheters within 1 hour after birth and thereafter alongwith every blood gas measurement. The results were correlated with the subsequent presence or absence of moderate-to-severe HIE by computing receiver operating characteristic curves.

RESULTS

The initial lactate levels were significantly higher (p=0.001) in neonates with moderate-to-severe HIE (mean+/-SD=11.09+/-4.6) as compared to those with mild or no HIE (mean+/-SD=7.1+/-4.7). Also, the lactate levels took longer to normalize in these babies. A plasma lactate concentration >7.5+/-mmol/l was associated with moderate-or-severe HIE with a sensitivity of 94% and specificity of 67%. The sensitivity and negative predictive value of lactate was greater than that of the pH or base deficit.

CONCLUSIONS

The highest recorded lactate level in the first hour of life and serial measurements of lactate are important predictors of moderate-to-severe HIE.

Vaginal breech delivery: is it still an option?

OBJECTIVE

To provide local data on term breech delivery for future guidance.

STUDY DESIGN

Retrospective, 'intended-mode-of-delivery' analysis of 711 antenatally uncomplicated singleton breech deliveries at >or=37 weeks: 445 (63%) planned for vaginal delivery (VD) (no fetal growth restriction, fetal weight 2000-4000 g, adequate pelvic size, maternal consent) and 266 for cesarean section (CS).

OUTCOME MEASURES

Apgar score, cord blood acid-base status, childhood deaths and disability.

RESULTS

Perinatal mortality was nil in both groups. Low 1-min Apgar scores and low arterial cord blood pH were significantly more frequent in planned VD, but not low Apgar scores at 5 or 10 min or low venous pH. Metabolic acidosis, neonatal intensive care, neonatal seizures, birth trauma, childhood death (CS=1), and neurodevelopmental handicaps (CS=2, VD=1) were equally common.

CONCLUSION

Our results do not disqualify selective vaginal breech delivery at term and beyond as an option.

Pulse oximetry during labour--does it give rise to hope? Value of saturation monitoring in comparison to fetal blood gas status

OBJECTIVE

Purpose of this presentation is to show the diagnostic power of fetal pulse oximetry in comparison to the other blood gas parameters from fetal blood samplings (FBS). The distribution of saturation readings in acidotic fetuses and normally oxygenated fetuses should be established.

STUDY DESIGN

A fetal pulse oximetry system (N400, FS14) was evaluated in a strictly observational study design based on blinded saturation display and on continuous data storing. The investigation was performed on 170 fetuses with non-reassuring fetal heart rate (FHR)-tracings. Since pulse oximetry readings were not available for decision finding, the clinical management was based on electronic fetal monitoring and fetal blood samplings. The oxygen saturation from FBS or umbilical cord blood was measured by blood gas analysers with an integrated hemoximeter (Bayer 865; ABL 625, Radiometer) and biosensors measuring lactate as metabolic component. Out of the 170 cases 17 cases were defined as group of acidemia (pH(umb.art.) < 7.16 + BD<-9.4). The distribution of saturation readings and the duration of desaturation periods (in minutes and percentage of total monitoring time SPO2 below 30%) were determined. ROC curve analysis from FBS preceding delivery compared the diagnostic power of other blood gas parameters with oxygen saturation. The Wilcoxon test for uneven pairs was used.

RESULTS

The distribution of oxygen saturation in the normal group of fetuses differs significantly from the acidemic group. The correlation coefficient between both methods to determine oxygen saturation was r=0.66. A specific evaluation of the distribution of SPO2 shows an overestimation of pulse oximetry in the low range and an underestimation in the high range of saturation. ROC-curve analysis showed a good diagnostic power of lactate in comparison to the oxygen saturation measured by pulse oximetry or by hemoximetry.

CONCLUSIONS

The advantage of continuous fetal pulse oximetry surveilling the fetus under suspicion of hypoxia appears limited by the poor diagnostic power of the respiratory parameter saturation itself and by the impairment of the precision of the technology.

Challenge of conducting trials of neuroprotection in the asphyxiated term infant

There has been much progress in understanding the pathogenesis of hypoxic-ischemic brain injury in the near-term and term infant. Although gaps in our knowledge base persist, advances over the past two decades have led to the development of specific brain oriented therapies directed at critical events contributing to tissue damage. The primary goal of these interventions is to prevent or attenuate neurologic and developmental sequelae of brain injury. Examples of current potential treatments include modest reductions in brain temperature, receptor antagonists of excitatory neurotransmitters, reductions in O2 free radicals, blockade of inflammatory mediators, and inhibition of apoptotic pathways. At present, some of these treatments have sufficient animal data that demonstrate benefit, to justify moving experiments from the laboratory to the clinical arena. Modest hypothermia represents the neuroprotective intervention that has been investigated in the most complete fashion for the newborn, and there are multiple ongoing clinical trials testing its efficacy. This review will address specific challenges that are pertinent to the evaluation of any neuroprotective therapy implemented shortly after birth. Specific issues to be covered include the therapeutic window, establishing a diagnosis of hypoxic-ischemic encephalopathy, patient selection, characteristics of an effective therapy, safety considerations, appropriate outcome variables, and sample size considerations. Since clinical trials of brain hypothermia are in progress, many of these issues will be addressed from the perspective of this specific intervention.

Use of umbilical artery base excess: algorithm for the timing of hypoxic injury

Intrapartum asphyxia is responsible for only a small proportion of cerebral palsy cases, although obstetricians are often held accountable. Umbilical cord pH and blood gas values provide valuable information regarding the status of the infant at birth; base excess determination quantifies the magnitude of metabolic acidosis, the putative risk factor for central neurologic injury. Human and animals studies have confirmed normal values of base excess before labor, and consistent rates of base excess change in relation to the degree of fetal hypoxemia or heart rate patterns. Thus, the combination of assumed base excess values before labor and measured values after birth, together with an assessment of degrees of fetal hypoxemia during labor, permits an interpolation of fetal base excess values throughout the course of labor. Because threshold levels of base excess (eg, -12 mmol/L) have been associated with an increased risk of neonatal neurologic injury, this approach provides a framework for the assessment of fetal heart rate tracings during labor and, potentially, the timing of hypoxic/ischemic injury.

Long-term developmental outcome of asphyxiated term neonates

Asphyxia remains one of the main causes of later disability in term infants. Despite many publications identifying possible predictors of outcome in this population of interest, little is known of the long-term developmental outcome of asphyxiated term neonates. Observational studies have largely focused on short-term outcomes, with an emphasis on significant neurologic sequelae and intellectual impairments. This article reviews the literature that has described the developmental outcome of asphyxiated term newborns. As part of this review, we have also highlighted the evolution of the definition of asphyxia and delineated appropriate markers that should be used in future research on this population.

Doppler velocimetry in the adrenal artery in human fetuses

BACKGROUND

Fetal hypoxia and/or acidosis causes redistribution of blood flow to the high-priority organs including the adrenal glands. Although this phenomenon is well described in the human cerebral and placental circulations using Doppler velocimetry, there are few reports about the adrenal glands.

AIM

To clarify the gestational age-related changes in adrenal blood flow in normal fetuses and fetuses at risk of hemodynamic derangement.

MATERIAL AND METHODS

In 153 normal cases, the resistance indices (RIs) calculated from the blood flow velocity waveforms (FVWs) in the middle adrenal artery (MAA) were obtained from 24 weeks to construct nomogram using regression analysis. Twenty-seven complicated cases were divided according to the 5%ile RI values in the MAA, and clinical outcomes were retrospectively compared.

RESULT

The RI values in the MAA increased until 31 weeks and decreased thereafter. The 50%ile regression curve was represented as RI=-0.000914 (weeks)(2)+0.0579 weeks-0.181. Of the 27 complicated cases, 13 had RIs in the MAA below the 5%ile. Cases with low RI had significantly higher RI ratio in regard of UA/MCA; higher occurrence of abnormal FHR patterns on observation; higher incidence of cesarean delivery for nonreassuring fetal well-being status; earlier gestational age at delivery; lower birth weights and longer periods of admission to NICU than the cases with normal RI.

CONCLUSION

We have described the nomogram for the RI in the MAA. In conditions of fetal hypoxia or acidemia, blood flow redistribution to the adrenal glands may occur and the analysis of the adrenal artery FVWs may be useful in detection of fetal altered hemodynamics.

Cardiotocography only versus cardiotocography plus ST analysis of fetal electrocardiogram for intrapartum fetal monitoring: a Swedish randomised controlled trial

BACKGROUND

Previous studies indicate that analysis of the ST waveform of the fetal electrocardiogram provides information on the fetal response to hypoxia. We did a multicentre randomised controlled trial to test the hypothesis that intrapartum monitoring with cardiotocography combined with automatic ST-waveform analysis results in an improved perinatal outcome compared with cardiotocography alone.

METHODS

At three Swedish labour wards, 4966 women with term fetuses in the cephalic presentation entered the trial during labour after a clinical decision had been made to apply a fetal scalp electrode for internal cardiotocography. They were randomly assigned monitoring with cardiotocography plus ST analysis (CTG+ST group) or cardiotocography only (CTG group). The main outcome measure was rate of umbilical-artery metabolic acidosis (pH <7.05 and base deficit >12 mmol/L). Secondary outcomes included operative delivery for fetal distress. Results were first analysed according to intention to treat, and secondly after exclusion of cases with severe malformations or with inadequate monitoring.

FINDINGS

The CTG+ST group showed significantly lower rates of umbilical-artery metabolic acidosis than the cardiotocography group (15 of 2159 [0.7%] vs 31 of 2079 [2%], relative risk 0.47 [95% CI 0.25-0.86], p=0.02) and of operative delivery for fetal distress (193 of 2519 [8%] vs 227 of 2447 [9%], 0.83 [0.69-0.99], p=0.047) when all cases were included according to intention to treat. The differences were more pronounced after exclusion of 291 in the CTG+ST group and 283 in the CTG group with malformations or inadequate recording.

INTERPRETATION

Intrapartum monitoring with cardiotocography combined with automatic ST-waveform analysis increases the ability of obstetricians to identify fetal hypoxia and to intervene more appropriately, resulting in an improved perinatal outcome.

Effect of extreme hypercapnia on hypoxic-ischemic brain damage in the immature rat

To ascertain the effect of extreme hypercapnia on perinatal hypoxic-ischemic brain damage, 7-d-postnatal rats were exposed to unilateral common carotid artery occlusion followed by hypoxia with 8% oxygen combined with 3, 12, or 15% carbon dioxide (CO2) for 2 h at 37 degrees C. Survivors underwent neuropathologic examination at 30 d of postnatal age, and their brains were characterized as follows: 0 = normal; 1 = mild atrophy; 2 = moderate atrophy; 3 = cystic infarct with external dimensions <3 mm; and 4 = cystic infarct with external dimensions >3 mm. The width of the cerebral hemisphere ipsilateral to the carotid artery occlusion also was determined on a posterior coronal section and compared with that of the contralateral hemisphere to ascertain the severity of cerebral atrophy/cavitation. CO2 tensions averaged 5.08, 11.1, and 13.2 kPa in the 3, 12, and 15% CO2-exposed animals, respectively, during hypoxia-ischemia (HI). Neuropathologic results showed that immature rats exposed to 3 and 12% CO2 had similar severities of brain damage. In contrast, rat pups exposed to HI combined with 15% CO2 were significantly more brain damaged than littermates exposed to 3% CO2. Specifically, eight of 14 animals exposed to 15% CO2 showed cystic infarcts (grades 3 and 4), whereas none of 14 littermates exposed to 3% CO2 developed cystic infarcts (p < 0.01). Analyses of coronal width ratios at each CO2 exposure provided results comparable with those of the gross neuropathology scores. Cerebral blood flow (CBF), measured at 90 min of HI, was lowest in those immature rats exposed to 15% CO2 compared with control (p = 0.04), with higher values in those rat pups exposed to 3 and 12% CO2. The findings indicate that 7-d-postnatal rats exposed to HI with superimposed 12% CO2 are neither less nor more brain damaged than littermates exposed to 3% CO(2) (normocapnia). In contrast, animals exposed to 15% CO2 are the most brain damaged of the three groups. Presumably, extreme hypercapnia produces more severe cardiovascular depression than is seen in animals subjected to lesser degrees of hypercapnia; the cardiovascular depression, in turn, leads to greater cerebral ischemia and ultimate brain damage.

Lactate measurements in scalp and cord arterial blood

Lactate has been measured to evaluate fetal metabolic acidosis for some decades. However, not until the past few years have reliable lactate meters become available for bedside obstetric practice. The new technology, which requires only 5 microl blood, has reduced the sampling failure rate of fetal scalp blood to almost nil. A growing body of evidence has also shown lactate to be good at predicting neonatal outcome.

Reproductive risk factors of fetal asphyxia at delivery: a population based analysis

To investigate reproductive maternal risk factors of intrapartum fetal asphyxia, we analyzed 556 women with singleton pregnancies complicated by intrapartum fetal asphyxia who gave birth at Kuopio University Hospital from January 1990 to December 1998. The general obstetric population (N=21746) was selected as the reference group and logistic regression analysis was used to identify independent reproductive risk factors. The incidence of intrapartum fetal asphyxia was 2.5%. Placental abruption, primiparity, alcohol use during pregnancy, low birth weight, preeclampsia, male fetuses, and small-for-gestational age births were independent risk factors of intrapartum asphyxia, with adjusted relative risks of 3.74, 3.10, 1.75, 1.57, 1.49, 1.48 and 1.33, respectively. Most cases of intrapartum fetal asphyxia occur in low-risk pregnancies and, therefore, risk screening in antenatal care cannot accurately predict which women will eventually need emergency care for fetal asphyxia.

Abnormal fetal cerebral and umbilical Doppler measurements in fetuses with intrauterine growth restriction predicts the severity of perinatal morbidity

PURPOSE

This prospective study was performed to determine if the ratio of the middle cerebral artery (MCA) S/D ratio (ratio of peak systolic blood flow velocity to diastolic velocity) to the umbilical artery (UA) S/D ratio (MCA/UA S/D ratio) predicts the degree of neonatal morbidity in fetuses suspected of having intrauterine growth restriction (IUGR).

METHODS

Sixty-one fetuses were identified prospectively by sonography as having an estimated fetal weight below the 10th percentile for gestational age. The 61 fetuses underwent Doppler sonography in the third trimester and then were stratified into 3 groups based on the MCA/UA S/D ratio: group A, MCA/UA S/D ratio > 1.0 (controls; n = 37); group B, MCA/UA S/D ratio < or = 1.0 (intracerebral blood flow redistribution; n = 16); and group C, reversed or absent UA diastolic flow (n = 8). Outcome variables assessed included gestational age at delivery, birth weight, UA pH, mode of delivery, respiratory distress syndrome requiring intubation, and intracranial hemorrhage.

RESULTS

The mean MCA/UA S/D ratios in groups A and B were 1.69 + /- 0.61 and 0.59 + /- 0.24, respectively (p < 0.01). The mean gestational ages at delivery for groups A, B, and C were 34.7, 33.2, and 29.0 weeks, respectively. The mean birth weights were below the fifth percentile for age for groups B and C and significantly related to the severity of abnormal Doppler findings (p < 0.01) after correction for age. Mean UA pHs were 7.25 + /- 0.01, 7.19 + /- 0.01, and 7.14 + /- 0.13 for groups A, B, and C, respectively, with significant differences between groups A and B (p < 0.05) and groups A and C (p < 0.05). Respiratory distress syndrome and intracranial hemorrhage were not associated with abnormal Doppler findings after correction for gestational age. The interval between the abnormal Doppler examination and delivery (p < 0.001) and the occurrence of fetal distress requiring cesarean section (p < 0.001) were significantly related to the severity of Doppler findings.

CONCLUSIONS

In fetuses with suspected IUGR, abnormal MCA/UA S/D ratios are strongly associated with low gestational age at delivery, low birth weight, and low UA pH. Abnormal MCA/UA S/D ratios are also significantly associated with shorter interval to delivery and the need for emergent delivery.

Antenatal predictors of the neurologic sequelae at 3 years of age: a multivariate analysis

OBJECTIVE

To study the association between fetal blood flow abnormalities and the occurrence of long-term neurologic sequelae.

STUDY DESIGN

Umbilical, aortic and middle cerebral artery blood flow parameters were obtained by Doppler examination and retrospectively analyzed in 128 high-risk singleton pregnancies, followed by neurologic examination of the surviving children at 3 years of age. Traditional parameters of neurologic outcome (Apgar scores, intrauterine growth retardation (IUGR), umbilical artery pH and base deficit, gestational age, birth weight, newborn encephalopathy, mode of delivery, fetal heart rate, neurosonographic examination) were included as possible confounding factors. Mann-Whitney U-test, Student's t-test, analysis of variance or Fisher's exact test, where applicable, were used for the univariate analysis. A stepwise logistic regression procedure was conducted to test the independent association of selected perinatal risk factors on neurological outcome. Statistical significance was assumed at P<0.05.

RESULTS

Eighteen out of 114 surviving children suffered neurologic illness at 3 years of age. Four children had major neurologic dysfunction and the remaining 14 suffered minor or mild form of the disease. Although blood flow parameters and various perinatal parameters did not differ significantly between the group of children with major neurologic dysfunction and healthy children, aortic resistance index showed an independent association with occurrence of minor or mild neurologic disabilities.

CONCLUSION

Antenatal evaluation of the aortic blood flow might be an important predictive variable for permanent neurologic disturbances.

Can neurological injury be timed?

Our knowledge about the cause of cerebral palsy continues to expand and prenatal events are thought to play an important role. This article reviews laboratory tests, imaging studies and pathologic findings that have been used to identify the timing of neurological injury. Limitations exist for all modalities, however, imaging studies, electroencephalograms and pathologic examination provide the most useful information. Improvements in our ability to time neurological injury will better direct our efforts to prevent cerebral palsy.

Outcome after successful resuscitation of babies born with apgar scores of 0 at both 1 and 5 minutes

OBJECTIVE

Our purpose was to evaluate the outcome of infants who underwent successful resuscitation after initial Apgar scores of 0 at both 1 and 5 minutes.

STUDY DESIGN

Eligible infants were identified through the perinatal database at the University of Tennessee, Memphis. Hospital records and long-term outcomes, where available, of babies who met the above criteria occurring between January 1986 and February 1999 were reviewed.

RESULTS

Thirty-three of 81,603 infants (0.4/1000 births) met our study criteria. Twenty-two (67%) babies died during hospitalization. Mortality decreased significantly from 100% for babies with a birth weight of <750 g to 38% for those weighing > or =2500 g at birth (P =.03). All 6 babies delivered before 26 weeks' gestation died. The incidence of 10-minute Apgar scores >0 was significantly higher among survivors than among those who subsequently died (82% vs 33%, P <.05). Nine survivors had hypoxic-ischemic encephalopathy diagnosed before discharge. Of the 7 infants with available follow-up, 4 had significant persisting morbidity. Two infants had normal neurologic examinations at follow-up.

CONCLUSION

Survival in babies born with 1- and 5-minute Apgar scores of 0 is predicted by birth weight, gestational age, and 10-minute Apgar score. Long-term sequelae are common but not ensured.

Fetal heart rate monitoring: is it salvageable?

Fetal heart rate monitoring was introduced in the 1960s. After a number of randomized controlled trials in the mid 1980s, doubt arose regarding the efficacy of fetal heart rate monitoring in improving fetal outcome. The potential reasons why fetal heart rate monitoring has not been shown to be efficacious are (1) use of an outcome measure that is not related to variant fetal heart rate monitoring patterns, (2) lack of standardized interpretation of fetal heart rate patterns, (3) disagreement regarding algorithms for intervention of specific fetal heart rate patterns, and (4) the inability to demonstrate the reliability, validity, and ability of fetal heart rate monitoring to allow timely intervention. A recent National Institutes of Health committee proposed detailed, quantitative, standardized definitions of fetal heart rate patterns, which can serve as a basis for determining whether fetal heart rate monitoring is reliable and valid. In this article we examine reasons why fetal heart rate monitoring did not live up to its original expectations and why the randomized controlled trials did not demonstrate efficacy, and we make suggestions for determining whether electronic fetal heart rate monitoring should be abandoned.

Intrapartum tocolysis has no effect on fetal lactate concentration

OBJECTIVE

To assess the fetal metabolic effects of intrapartum maternal tocolysis with terbutaline in the presence of fetal heart rate abnormalities, with a special emphasis on lactate concentration, in view of its potential use as a marker of fetal condition.

DESIGN

Descriptive study.

SETTING

Two labour wards, National University Hospital, Singapore, and Ostersund Hospital, Sweden.

METHODS

Eight parturients with abnormal intrapartum fetal heart rate recordings were given bolus i.v. injection of 0.25 mg terbutaline and monitored both before and 20 minutes after treatment.

RESULTS

Maternal venous glucose increased from 5.0 (0.9) (mean (SD)) to 5.6 (1.2) mmol/l (p=0.002) and fetal scalp blood glucose rose from 4.1 (1.8) to 4.7 (1.4) mmol/l (p=0.009) 20 minutes after the injection. No significant change was found in maternal or fetal lactate concentrations.

CONCLUSION

Terbutaline tocolysis for "intrauterine resuscitation" does not affect fetal lactate concentration 20 minutes after treatment.

Intrapartum fetal surveillance

Intrapartum hypoxia was thought to contribute to the incidence of cerebral palsy, seizures and mental retardation. Electronic fetal monitoring was expected to prevent or reduce this incidence. Electronic fetal monitoring has a high false positive rate and fetal blood sampling, which is an invasive procedure, only allows an intermittent assessment. Efforts are being made to improve fetal heart rate analysis and clinical management. Fetal pulse oximetry, fetal electrocardiogram waveform analysis and the intermittent measurement of lactate levels by fetal blood sampling may become established as an adjunct to electronic fetal monitoring.

Intrapartum Fetal Surveillance. Is It Worthwhile?

Potentially significant intrapartum fetal asphyxia occurs in approximately 20 per 1000 births. Moderate and severe fetal asphyxia exposure with newborn morbidity occurs in 3 to 4 1000 births, with brain damage and subsequent disability in at least 1 per 1000 births. Although the prevalence of moderate and severe asphyxia is modest, prevention is important because of the serious implications of this complication to the child, family, and society. Because of the limited predictive value of clinical risk factors, the interpretation of patterns in a fetal heart rate record has become the primary screening test for intrapartum fetal asphyxia. Despite extensive clinic experience and numerous clinical trials, the benefits of EFM as a screening test have not been established, and harm may occur owing to unnecessary intervention. This observation raises serious ethical issues. When an intervention is initiated by the clinician rather than the patient, the clinician under greater obligation to ensure that the benefits outweigh the harm. Several factors complicate the demonstration of benefits of EFM as a screening test. There is no consensus regarding a protocol of fetal surveillance for low-risk patient who account for approximately 25% of intrapartum fetal asphyxia. Moderate and severe asphyxia cannot be prevented when asphyxial exposure has occurred before labor or before the onset of fetal surveillance. Prediction of intrapartum fetal asphyxia cannot occur when the quality of the record does not permit interpretation. Interpretation of predictive fetal heart rate patterns cannot occur unless the record is consistently and carefully scored. Prediction of most cases of intrapartum fetal asphyxia on the basis of fetal heart rate patterns is possible but difficult. Because the goal of intrapartum fetal surveillance is the prevention of moderate and severe fetal asphyxia, prediction must be achieved before fetal decompensation. Prediction must occur before absent baseline fetal heart rate variability evident in the record, which is uniformly associated with cerebral dysfunction and, in some cases, brain damage. The possibility of fetal asphyxia must be considered when, within a 1-hour window of recording, there are two or more cycles of minimal baseline fetal heart rate variability and two or more cycles of late or prolonged decelerations or both. Because approximately 9 of 10 predictive fetal heart rate patterns are false-positive, supplementary tests to confirm the diagnosis and to identify false-positives to prevent unnecessary intervention are essential. Until such time as additional fetal assessment tests are validated, blood gas and acid-base assessment of fetal blood can provide a definitive diagnosis and identify false-positive predictions.

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.

Association between umbilical blood gas parameters and neonatal morbidity and death in neonates with pathologic fetal acidemia

OBJECTIVE

Our purpose was to correlate umbilical artery blood gas parameters with neonatal death and indicators of morbidity in neonates with pathologic fetal acidemia (pH <7.0).

STUDY DESIGN

We reviewed maternal and neonatal charts of 93 neonates with an umbilical artery pH <7.0 who were delivered at 2 university-based centers. The relationships between umbilical artery pH, PO (2), PCO (2), bicarbonate, base deficit, and neonatal variables-death, need for intubation, cardiopulmonary resuscitation, seizures, hypoxic-ischemic encephalopathy, respiratory distress syndrome, intraventricular hemorrhage, meconium, sepsis, and intrauterine growth restriction-were determined with the Student t test, Mann-Whitney U test, and multiple logistic regression analysis. Data are presented as either median with 25th-75th percentiles or mean +/- SD.

RESULTS

The mean gestational age at delivery was 37.9 +/- 3. 6 weeks, and the mean birth weight was 3003 +/- 866 g. There was no relationship between neonatal death, respiratory distress syndrome, intraventricular hemorrhage, necrotizing enterocolitis, patent ductus arteriosus, meconium, sepsis, and any umbilical artery blood gas parameter. The PO (2) was not related to any of the variables studied. A lower umbilical artery pH was associated with hypoxic-ischemic encephalopathy (6.69 vs 6.93, P =.03), cardiopulmonary resuscitation (6.83 vs 6.93, P =.03), seizure (6.75 vs 6.93, P =.02), intubation (6.83 vs 6.94, P <.001), and intrauterine growth restriction (6.72 vs 6.93, P =.01). Greater mean base deficit was associated with seizure (20.6 vs 15, P =.01), intubation (18.0 vs 13.7, P <.001), cardiopulmonary resuscitation (18.5 vs 15.0, P =.03), intrauterine growth restriction (22.0 vs 14. 0, P =.02), and hypoxic-ischemic encephalopathy (24.0 vs 14.5, P =. 03). Arterial PCO (2) was higher only in infants with hypoxic-ischemic encephalopathy (138 vs 95.5, P =.048), intubation (106.0 vs 90.5, P =.003), and cardiopulmonary resuscitation (106.5 vs 93.0, P =.04). After control for birth weight and gestational age in the multivariate analysis, base deficit and bicarbonate were independently related to death or morbidity.

CONCLUSION

Our data suggest that "pathologic" fetal acidemia is indicated by an umbilical artery pH <7.00 with a metabolic component. The metabolic component of fetal acidemia (ie, base deficit and bicarbonate) is the most important variable in subsequent neonatal morbidity. As expected, the umbilical artery PO (2) has no apparent clinical utility. The ability to predict more accurately which newborn infants with fetal acidemia are at risk of having complications may lead to a more efficient implementation of preventive measures.

Antepartum computerized CTG and neonatal acid-base status at birth

OBJECTIVE

To assess the correlation between individual computerized cardiotocography (cCTG) variables and acid-base status at birth before the first breathing in uncomplicated term pregnancy delivered by cesarean section.

STUDY DESIGN

A retrospective cohort study.

SUBJECTS AND METHODS

Seventy singleton normal pregnancies delivered by elective cesarean section. The last antepartum cCTG performed within 4 h from delivery by the System 8002 (Oxford Sonicaid, UK) was correlated to umbilical blood gas analysis (UBGA) values (AVL compact 2 analyser). Considering blood gas analysis values as dependent and individual cCTG parameters as independent variables the best regression subsets followed by a backward stepwise linear regression was used.

RESULTS

There was no significant correlation of cCTG parameters with any of the values of blood gas analysis. However, when neonatal conditions, as expressed by arterial pH > 7.20, Becf > - 4.0 mmol/l and Apgar score at 5 min > 7, were taken as an end-point, they could be predicted by Acc15 and FM/hour (sensitivity: 35%, positive predictive value: 92%, cut-off > 7 and 67%, 92%, > 21, respectively).

CONCLUSION

In uncomplicated pregnancies, the prospect of a vigorous newborn seems particularly associated with the presence of Acc > 15 and FM/hour > 21.

A new method for rapid measurement of lactate in fetal and neonatal blood

A prospective trial to determine the accuracy and precision of the Boehringer Mannheim Accusport handheld lactate meter in measuring plasma lactate levels in umbilical cord blood and neonatal blood microsamples was performed in the labour ward and the neonatal intensive care unit of the NepeanHospital. Specimens were collected from the umbilical artery of 160 consecutive deliveries covering gestations from 26 to 42 weeks, and from 110 umbilical artery catheters covering a range of gestations from 26 to 41 weeks. Serum was also obtained from an exchange transfusion for coefficient of variation analysis. Blood was simultaneously tested for lactic acid concentration on the Boehringer Mannheim (BM) Accusport held lactate meter and the Radiometer ABL 625 blood-gas machine. Clinical data from the mother and baby were recorded together with the full blood-gas analysis for comparison with the lactate measures. Coefficients of variation for the BM Accusport lactate meter were established by a further 120 samples of plasma lactate at 6 concentrations from 1 to 20 mmol/L. The stability of measurements with the BM lactate meter over a wide range of temperatures was ascertained by repeated sampling of known concentrations of plasma lactate from 0.5 degrees C to 37 degrees C. The BM Accusport lactate meter was found to be accurate from 1 mmol/L to 20 mmol/L with a Passing Bablok regression line y = 0.004 + 0.915 x (95% CI of slope of 0.889 to 0.946 and intercept -0.138 to 0.094) for whole blood, and y = 0.200 + 1.000 x (95% CI of slope 0.989 to 1.018 and intercept 0.080 to 0.222) for plasma. Between run coefficient of variation (CV) was calculated to be 1.23% to 5.53% over the clinically significant range (2.2-19.3 mmol/L). The BM lactate meter was accurate from 5 to 37 degrees C. At 0.5 degrees C the BM lactate meter significantly underestimated the plasma lactate concentration. There was no significant effect of haematocrit (41.5 to 62%), gestation, or operator on the accuracy of the BM lactate meter. The Accusport handheld lactate meter is an accurate, commercially available, method of measuring plasma lactate levels in only 60 seconds at the point-of-care. It requires only 15 microL of blood and is significantly cheaper than other assay methods. The BM lactate meter is well suited to assess lactic acidaemia of fetal scalp and neonatal blood samples to help quantify hypoxic stress in the perinatal period.

Intrapartum fetal hypoxia and biochemical markers: a review

Intrapartum fetal hypoxia is a rare event, although fetal intrapartum surveillance is discussed as a subject of major importance. This is mainly because of consequences of fetal hypoxia that may lead to cerebral palsy. A fetus suffering from hypoxia initially compensates by producing energy through anaerobic metabolism. At some stage, the fetus becomes decompensated and basic cellular functions fail, with risks of permanent morbidity or mortality. How long a fetus can survive on anaerobic metabolism differs because metabolic reserves differ, i.e., growth-restricted fetuses might deteriorate at an earlier stage. An increasing body of evidence has clarified brain-damaging mechanisms. Neuronal loss occurs in two phases: during the primary hypoxic event and later during the reperfusion/reoxygenation phase. Animal studies have suggested the possibility of prophylactic treatment to prevent neuronal loss after the hypoxic event. Intrapartum diagnostic tools should aim for detecting fetal hypoxemia/hypoxia when the fetus is still compensated. This may be achieved by assessment of biochemical data such as pH, lactate, and oxygen saturation, with the aim of prophylactic intervention before the fetus becomes decompensated. The measurement of cord blood levels of oxygen free radicals and excitatory amino acids at the time of birth may prove to be helpful in determining the risk of brain damage and evaluating the effect of prophylactic treatments to prevent or ameliorate brain injury from hypoxia.