Fetal distress and the condition of newborn infants

Automatic classification of fetal heart rate based on a multi-scale LSTM network

Introduction

Fetal heart rate monitoring during labor can aid healthcare professionals in identifying alterations in the heart rate pattern. However, discrepancies in guidelines and obstetrician expertise present challenges in interpreting fetal heart rate, including failure to acknowledge findings or misinterpretation. Artificial intelligence has the potential to support obstetricians in diagnosing abnormal fetal heart rates.

Methods

Employ preprocessing techniques to mitigate the effects of missing signals and artifacts on the model, utilize data augmentation methods to address data imbalance. Introduce a multi-scale long short-term memory neural network trained with a variety of time-scale data for automatically classifying fetal heart rate. Carried out experimental on both single and multi-scale models.

Results

The results indicate that multi-scale LSTM models outperform regular LSTM models in various performance metrics. Specifically, in the single models tested, the model with a sampling rate of 10 exhibited the highest classification accuracy. The model achieves an accuracy of 85.73%, a specificity of 85.32%, and a precision of 85.53% on CTU-UHB dataset. Furthermore, the area under the receiver operating curve of 0.918 suggests that our model demonstrates a high level of credibility.

Discussion

Compared to previous research, our methodology exhibits superior performance across various evaluation metrics. By incorporating alternative sampling rates into the model, we observed improvements in all performance indicators, including ACC (85.73% vs. 83.28%), SP (85.32% vs. 82.47%), PR (85.53% vs. 82.84%), recall (86.13% vs. 84.09%), F1-score (85.79% vs. 83.42%), and AUC(0.9180 vs. 0.8667). The limitations of this research include the limited consideration of pregnant women's clinical characteristics and disregard the potential impact of varying gestational weeks.

Impact of social violence and childhood adversities on pregnancy outcomes: a longitudinal study in Tunisia

Background

Accumulating research suggests that exposure to intra-familial adversities are significant risk factors for adverse pregnancy outcomes. However, the relationship between social violence (peer violence, witnessing community violence and exposure to collective violence) and pregnancy outcomes has not been extensively investigated. Our study aims to examine the association between social Adverse Childhood Experiences (ACEs) and pregnancy outcomes and to explore the role of depression during pregnancy as a mediator of this association.

Methods

We performed a prospective follow-up study of pregnant women in five Primary Health care Centers (PHC) in the region of Monastir (Tunisia) from September 2015 to August 2016. Enrolled women were followed during the second trimester, third trimester of pregnancy and during the postnatal period. Exposure to violence was assessed retrospectively using the validated Arabic version of the World Health Organization (WHO) ACE questionnaire. The Self Reporting Questionnaire 20-Item (SRQ-20) was used as a screening tool for depression during pregnancy.

Results

We recruited and followed a total of 593 women during the study period. Witnessing community violence was the most frequently reported social ACE among pregnant women (237; 40%), followed by peer violence (233; 39.3%). After adjustment for high risk pregnancies, environmental tobacco smoke, and intra-familial ACEs, the risk of premature birth was significantly associated with exposure to collective violence (P < 0.001) and witnessing community violence (P < 0.05). The risk of low birth weight was significantly associated with witnessing community violence (P < 0.001). In the mediation analysis, depression mediated significant proportions of the relationship between the cumulative number of ACEs and pregnancy outcomes.

Conclusions

Social ACEs may have a long-term effect on maternal reproductive health, as manifested by offspring that were of reduced birth weight and shorter gestational age. A public health framework based on the collaboration between pediatric, psychiatric obstetrical health professionals, education professionals and policy makers could be applied to ensure primary prevention of childhood adversities and pay attention to expected mothers with history of exposure to such adversities.

Reference percentiles for paired arterial and venous umbilical cord blood gases: An indirect nonparametric approach

BACKGROUND

Reference intervals for arterial and venous umbilical cord blood gas (UCBG) parameters are scarce, are mainly focused on pH, pO2, pCO2 and base deficit, and are usually assessed using parametric tests, despite a generally skewed data distribution. Here, the purpose is to determine reference percentiles for nine parameters of concomitant arterial and venous UCBG (CAV-UCBG) from neonates at birth, using nonparametric tests.

METHODS

Results of CAV-UCBG, assayed over a 4.5-year period, were extracted from a hospital laboratory database for pH, pCO2, pO2, oxygen saturation, concentration of total oxygen, total carbon dioxide, hydrogen carbonate, total haemoglobin, and acid-base excess. Exclusion criteria were: a venous-arterial pH difference <0.02, an arterial-venous pCO2 <0.7 kPa, and a venous pCO2 <2.9 kPa. Nonparametric bivariate kernel density estimations were used for the selection of plots within the 95% percentile surface of the pCO2-to-pH relationship (NBKDE-95P). Outliers from skewed data were removed using an adjusted-Tukey method, and percentiles were calculated according to the CLSI EP28-A3 nonparametric method.

RESULTS

Overall, 31% (5033/16164) of CAV-UCBG were discarded using the three exclusion criteria. Then, 6% (670/11131) of CAV-UCBG were excluded from the NBKDE-95P, and 0.1 to 3.5% outliers were subsequently removed. Depending on the parameter, the 2.5th and 97.5th percentiles from the whole group were similar or slightly narrower compared to reference intervals from other studies, while those from female and male neonates did not differ substantially.

CONCLUSIONS

Using an indirect nonparametric approach, this study proposes new percentiles for parameters from concomitant arterial and venous umbilical cord blood gases.

First do the experiment: Do computerised interpretation of cardiotocography and other widely used interventions improve newborn outcomes?

The introduction of continuous electronic fetal heart rate monitoring (EFM) in labour has coincided with a steady and remarkable fall in perinatal mortality. Whether this is cause or coincidence remains unclear because randomised trials have been underpowered. Attempts to improve the sensitivity and specificity of fetal compromise detection using fetal blood sampling and pH measurement, pulse oximetry, and fetal electrocardiogram analysis have failed to provide evidence of additional value in randomised trials. Recently, litigation to obtain compensation for obstetric and midwifery error, often reported to be failure to recognise abnormal EFM traces, has escalated. The hypothesis that computerised heart rate pattern recognition could reduce adverse outcomes was tested in a randomised controlled trial of 46,000 labours but showed no benefit. It seems that complicating risk factors such as fetal growth restriction, meconium liquor, pyrexia in labour, and excessive use of oxytocin, are more important than previously realised.

Newborn outcomes in british columbia after caesarean section for non-reassuring fetal status

OBJECTIVE

To assess the incidence in British Columbia of severe morbidity in neonates delivered by Caesarean section for non-reassuring fetal status, and to examine the accuracy of Apgar score and umbilical cord gas values in predicting severe neonatal morbidity.

METHODS

We assessed rates of hypoxic ischemic encephalopathy, NICU admission, and ventilator days, individually and as a composite outcome with neonatal death, among a total of 8466 term singletons delivered by Caesarean section for non-reassuring fetal status between January 1, 2007, and December 31, 2011. We calculated the predictive accuracy of Apgar scores and umbilical cord blood gas values using the area under the receiver operating characteristic (ROC) curve and the sensitivity and specificity for each outcome.

RESULTS

The incidence of Apgar score at one minute < 4 was 8.0%, and for Apgar score at five minutes < 4 it was 0.6%. The incidence of umbilical cord pH < 7.10 was 6.5%, and for base-excess < -12 it was 2.9%. Apgar score at one minute < 7 had the greatest predictive accuracy for the composite outcome (81% for both sensitivity and specificity). The area under the ROC curve for Apgar score at one minute and at five minutes, umbilical cord pH, and base-excess was 0.87, 0.86, 0.76, and 0.78, respectively.

CONCLUSION

The incidence of abnormal Apgar score and abnormal umbilical cord gas values is very low among neonates in British Columbia delivered by Caesarean section for non-reassuring fetal status. Apgar score at one minute < 7 is a good predictor of severe neonatal morbidity. Electronic fetal monitoring remains a non-specific method for detection of fetal compromise in the intrapartum period.

Perinatal morbidity and risk of hypoxic-ischemic encephalopathy associated with intrapartum sentinel events

OBJECTIVE

To examine perinatal morbidity and rate of hypoxic-ischemic encephalopathy in infants exposed to intrapartum sentinel events.

STUDY DESIGN

Retrospective cohort study from 2000-2005. Perinatal mortality, perinatal morbidity and rate of hypoxic-ischemic encephalopathy were compared in 3 groups of infants exposed to different risk factors for perinatal asphyxia (sentinel events, nonreassuring fetal status, elective cesarean section).

RESULTS

Five hundred eighty-six infants were studied. Perinatal mortality was 6% in the sentinel event group and 0.3% in the nonreassuring fetal status group (relative risk, 2.4; 95% confidence interval, 1.95-2.94). Perinatal morbidity was 2-6 times more frequent in infants exposed to sentinel events; the incidence of hypoxic-ischemic encephalopathy was 10%, compared with 2.5% in the nonreassuring fetal status group (relative risk, 1.93; 95% confidence interval, 1.49-2.52). No infant in the elective cesarean section group died, had perinatal morbidity, or developed encephalopathy.

CONCLUSION

Intrapartum sentinel events are associated with a high incidence of perinatal morbidity and hypoxic-ischemic encephalopathy.

Surveillance during labour

The technology of intrapartum surveillance made rapid strides from the 1960s through the 1980s but then stagnated as increasing resort to caesarean section was made rather than improving measures of fetal condition and labour progress. However, despite caesarean section rates commonly over 30%, medicolegally expensive mistakes continue to be made because it is difficult to teach clinicians to make reliable use of existing technology. It may be that as with aircraft navigation, the safest solution is to replace human judgement with the obstetric equivalent of automatic pilots.

Intrapartum management of nonreassuring fetal heart rate patterns: a randomized controlled trial of fetal pulse oximetry

OBJECTIVE

We tested if fetal pulse oximetry in addition to electronic fetal monitoring (CTG) and scalp blood sampling improves the accuracy of fetal assessment and allows safe reduction of operative deliveries (-50%) and scalp blood sampling (-50%) performed because of nonreassuring fetal status. Study design A randomized controlled trial was conducted in 146 patients with term pregnancies in active labor and abnormal fetal heart rate patterns: 73 had electronic fetal heart rate monitoring (CTG) and fetal scalp blood sampling (control group), 73 had CTG, fetal scalp blood sampling, and continuous fetal pulse oximetry (study group).

RESULTS

There was a reduction of -50% in operative deliveries and fetal scalp blood sampling performed because of nonreassuring fetal status in the study group: operative deliveries, study versus control 25/49 (P </= .001); fetal scalp sampling, study versus control 32/64 (P </= .001). An increase in cesarean sections because of dystocia in the study group did not change the net number of operative deliveries. There was no difference between the 2 groups in adverse maternal or neonatal outcomes, as well as for the end points of metabolic acidosis and need for resuscitation.

CONCLUSION

There was a safe reduction in operative deliveries (-50%) and scalp blood sampling (-50%) performed because of nonreassuring fetal status. The increase in cesarean sections because of dystocia in the study group was a well-documented arrest of labor, but it did not change the total number of operative deliveries in this group.

Clinical usefulness of pulse oximetry in the fetus with non-reassuring heart rate pattern?

The objective of this study was the evaluation of intrapartum pulse oximetry as an indicator of fetal distress and the condition of the newborn during clinical routine surveillance in an University Perinatal Center. Between 1998 and 1999 pulse oximetry (SpO2) was used additionally to routine fetal monitoring by electronic fetal heart rate tracing (CTG) and fetal blood sampling (FBA) in 128 cases with nonreassuring heart rate pattern. Cut off values were FIGO Score < 8 for the heart rate pattern and for fetal blood sampling during labor results of < 7.25 (preacidosis). The condition of the newborn was defined by the APGAR score with the cut off < 7 at 1 minute, while the biochemical status was evaluated by means of arterial blood sampling of the umbilical artery directly after birth using a pH of < 7.20 to verify acidosis. Predictive values of critically low SpO2 values (< 30%) for at least 10 minutes as well as corresponding sensitivities and specificities were calculated together with 95% confidence intervals to identify fetal distress or a depressed condition of the newborns. Of 128 fetuses included in this study 66 (52%) were born spontaneously, 23 (18%) were born by operative vaginal delivery and 39 (31%) by means of cesarean section. The high rate of cesarean section was due to cephalopelvic disproportion in 29 cases. Fetal outcome was evaluated with a clinical score: mean APGAR score value 8.5 SD +/- 1. The mean value of the pH in the umbilical artery was 7.23 +/- 0.04. During a SpO2 monitoring period of 18,381 minutes we analyzed a contact time of 63%. Comparing SpO2 values of < 30% with preacidosis in the fetal blood sampling, we found a positive predictive value of merely 0.17 (95% CI: 0.00-0.64). Of 9 preacidotic cases during delivery only 1 was indicated by a saturation value below 30% (sensitivity 0.11, 95% CI: 0.00-0.48). The specificity and negative predictive value were calculated as 0.83 (95% CI: 0.65-0.94) and 0.76 (95% CI: 0.58-0.89) respectively. Of eleven cases with acidosis in the blood of the umbilical cord artery, pH < 7.20, only 2 were indicated by a SpO2 values below 30%. Which is equivalent to a sensitivity of 0.18 (95% CI: 0.03-0.52). Results of a receiver operator curve analysis showed no substantial deviation from the diagonal. The area under the curve was 0.62, the 95% CI (0.47-0.76) indicating no significant discrimination. Three of 49 fetuses with SpO2 recording during the last 10 minutes were born in clinical depressed status (APGAR < 7). None was indicated by a SpO2 value below 30%.

CONCLUSION

Fetal distress and impaired condition of the newborn are not identified or predicted during routine application of SpO2 monitoring in the fetus during labor with adequate safety.

Doppler ultrasonographic evidence of intrapartum brain-sparing effect in fetuses with low oxygen saturation according to pulse oximetry

OBJECTIVE

This study was undertaken to verify by means of Doppler ultrasonography and simultaneous fetal pulse oximetry the redistribution of fetal blood flow in favor of the brain during intrapartum hypoxemia.

STUDY DESIGN

During labor 11 term fetuses with abnormal heart rate patterns and arterial oxygen saturation <30% and 14 control term fetuses with normal oxygen saturation were simultaneously monitored by pulse oximetry and Doppler ultrasonography. The results were compared with the Student t test.

RESULTS

The blood flow velocity in the middle cerebral artery was significantly higher in the presence of reduced oxygen saturation, implying lower pulsatility and resistance indices (P <.001). The reduction of blood flow in the umbilical artery was not significant (P =.61).

CONCLUSION

Simultaneous intrapartum pulse oximetry and Doppler ultrasonography proved that reduced arterial oxygen saturation (<30%) is associated with profound changes in fetal hemodynamics and could be tolerated for only a limited period, which should be the subject of further studies.

The incidence of abnormal findings from intrapartum cardiotocogram monitoring in term and preterm labours

A retrospective analysis of 514 consecutive labours delivering 530 babies over a period of 18 months was conducted by a high-risk pregnancy team in a tertiary teaching unit to compare the incidence of abnormal findings from intrapartum monitoring between labours occurring before and at or after 34 weeks' gestation. Those delivered by elective Caesarean section, or Caesarean section at the onset of labour because of contraindications to labour and vaginal delivery, and those with congenitally malformed fetuses were excluded. Tracings were scored using the FIGO 1987 guidelines. Seventy-four labours and 83 babies delivered before 34 weeks, and 440 labours and 447 babies delivered after 34 weeks in the study. There was a slightly higher incidence of suspicious CTG tracings (33.7% versus 19.6%, OR 2.66, 95% CI 1.6-4.4) in the preterm group, due mainly to decreased baseline variability (p<0.001, OR 3.57, 95% CI 1.8-6.9), but the incidence of other pathological patterns did not differ. Using the same set of criteria for interpretation, there was a higher incidence of abnormalities from continuous cardiotocogram monitoring in the preterm group compared to term labours, but the intervention rate for fetal distress was not significantly increased. Appropriate interpretative criteria for intrapartum monitoring of preterm labours should be devised.

Lactate compared with pH analysis at fetal scalp blood sampling: a prospective randomised study

OBJECTIVE

Fetal scalp blood sampling is a widely used method for assessing fetal condition in the event of ominous fetal heart rate patterns. The purpose of this randomised trial was to compare the value of fetal scalp blood lactate and pH management in cases of abnormal intrapartum fetal heart rate tracings.

METHODS

Of 341 cases of ominous fetal heart rate patterns, 169 were randomly assigned to pH analysis, and 172 to lactate measurements. Lactate was measured using a lactate card requiring 5 microL of blood and yielding the result within 60 seconds. pH analysis was performed with an ABL 510 acid-base analyser requiring 35 microL of blood and yielding the results within 47 seconds.

RESULTS

Unsuccessful fetal blood sampling procedures (no result or an unreliable result) occurred significantly more often in the pH subgroup than in the lactate subgroup (OR 16.1 with 95% CI 5.8-44.7). In the pH subgroup the failure rate was inversely related to the degree of cervical dilatation. Compared with the pH subgroup, the lactate subgroup was characterised by fewer fetal scalp incisions per blood sampling attempt (median 1.0 [interquartile range (IQR) 1-1] vs 2.0 [IQR 1-2]), and significantly less time required for the sampling procedure (median 120 s [IQR 90-147] vs 230 s [IQR 180-300]). The groups did not differ in mode of delivery, neonatal outcome and umbilical artery acid-base balance and lactate levels.

CONCLUSION

This trial showed the levels of lactate and pH in fetal scalp blood to be comparable in predicting perinatal outcome, but the procedure to measuring lactate was more successful than that for pH. Owing to its simplicity of performance, lactate analysis is an attractive alternative for intrapartum fetal monitoring.

The potential impact of PR interval analysis of the fetal electrocardiogram (FECG) on intrapartum fetal monitoring

A retrospective study was performed at the Queens Medical Centre, Nottingham, UK to evaluate the potential value of PR interval analysis of the FECG compared to conventional intrapartum assessment with fetal heart rate monitoring. Two-hundred sixty-five labours were selected for monitoring. Outcome was assessed by the number of fetal scalp blood samples (FBS) performed and the associated incidence of acidosis in the first stage of labour, the mode of delivery and whether or not this was expedited for fetal heart abnormality or an abnormal scalp pH. The condition of the fetus at delivery was assessed by arterial and venous blood acid-base status, Apgar score and the need for admission to the neonatal intensive care unit. Conventional electronic fetal heart rate monitoring (EFM) was used in all labours. The addition of PR interval assessment would potentially reduce the numbers of normal FBSs being carried out from 85.5% to 26.8% and the proportion of cases of missed acidosis at delivery from 8.5% to 4.5%. These results highlight the potential benefit of PR interval analysis in improving interpretation of the intrapartum cardiotocograph and need to be tested by prospective randomised controlled study.

Monitoring technology and the clinical perspective

Currently available technology requires a new look to reduce intervention as well as to improve the detection of the truly at-risk fetus. Iatrogenic causes of so-called fetal distress, in particular the administration of uterotonics without due attention to avoiding hyperstimulation, predominate as a reason for intervention. There needs to be a better definition of the starting point, i.e assessment of the fetal condition and identification of any risk factors, such as oligohydramnios and growth retardation, that might diminish fetal reserve. This will allow 'customization' of surveillance and management according to the needs of each individual fetus. There also needs to be better training and better agreement about the end-point of monitoring. For prospective surveillance, the aim is to avoid rather than to identify damage, and the definition of the appropriate point for intervention needs to come from better consensus on what is and what is not acceptable management based on current knowledge. New technology holds the promise that it can give trended information during labour, allow early recognition of problems and reduce unnecessary intervention. However, there is a need to ensure reliability and reproducibility of the readings before a new method is released. Co-operation with industry is essential, but the roles need to be well defined and the ultimate responsibility for establishing the role of a new technique has to come from the clinicians involved in intrapartum care.

On intrapartum fetal monitoring

The currently advised conduct for intrapartum surveillance of the fetus is either intermittent auscultation of continuous electronic monitoring, depending on the physician's preference. This applies to all, normal or high-risk, conditions. The bases for this recommendation, a number of controlled studies comparing the two methods, showed no better neonatal outcomes and increased cesarean section rates with electronic fetal monitoring. A review of the works pertaining to fetal development of cardiovascular and central nervous systems and their response to various pathophysiologic conditions (in animals and humans) was carried out in an effort to find an explanation for this apparently uncongruous position. It was found that fetal responses to seemingly comparable conditions are radically different depending on age of gestation. Many authors have pointed this out for the human fetus. However, for interpretation of electronic fetal monitoring in labor, various standard, nondescriptive, confusing words are used to imply the need for rapid intervention. The complete lack of uniform interpretation has been shown in studies comparing interobserver and intraobserver variations. This may be the consequence of poor or superficial teaching of a tool that requires much study and hard work for useful application. The inescapable conclusion is unpleasant but inevitable: to use electronic fetal monitoring properly it is necessary to start a new learning of the physiology of the fetus, its changing evolution as pregnancy advances, its different responses under stress or distress, and the various ways these are represented in electronic fetal monitoring tracings. These efforts take dedication and time spent in labor suites collating tracings with neonatal condition. Only by doing this will it be possible to assist the laboring patients with a useful tool that, so far, has not been adequately applied because of insufficient understanding.

Variation in caesarean and instrumental delivery rates in New Zealand hospitals

A study of Caesarean section and instrumental delivery rates in the maternity hospitals in New Zealand delivering over 1,000 women per year was undertaken. The results at Middlemore Hospital were compared with those seen elsewhere. The Caesarean section rate at Middlemore Hospital in 1993 was significantly lower than the other large maternity hospitals in New Zealand. The Caesarean section rate at Middlemore from 1988 to 1993 has shown a significant downward trend which is different from the trends at other hospitals. The spontaneous vaginal delivery rates at Middlemore Hospital were higher than at other New Zealand hospitals between 1988 and 1993. We conclude that Middlemore Hospital has been successful in maintaining low interventional delivery rates by New Zealand and international standards--the Caesarean section rate remains below 10% and the spontaneous vaginal delivery rate approaches 85%. This is likely to be a consequence of a number of factors operating together but there is evidence to suggest that obstetric management policies at Middlemore do play a role in this.

The T/QRS ratio of the electrocardiogram does not reliably reflect well-being in fetal lambs

OBJECTIVE

Our purpose was to determine the diagnostic power of the T/QRS ratio of the electrocardiogram to predict fetal well-being.

STUDY DESIGN

In 47 fetal lambs (3 to 5 days after surgery, gestational age 123.5 +/- 3.0 days) asphyxia was induced by restriction of uterine perfusion. Fetuses were either pretreated with an adenosine transport inhibitor (n = 16) or a calcium channel blocker (n = 12) or served as controls (n = 19). Arterial oxygen content > or = 1.5 mmol/L or pH > or = 7.15 were chosen as limits for fetal well-being.

RESULTS

Arterial oxygen content was reduced from 3.3 (+/- 1.0) to 1.3 (+/- 0.5) mmol/L, and pH decreased to 7.03 (+/- 0.10). Mortality was 53%. Both drugs did not affect well-being, survival, or the T/QRS ratio. Maximum T/QRS ratios were reached at the peak of asphyxia. Sensitivity and specificity of the T/QRS ratio were 24.0% and 42.6% to predict hypoxemia and 25.1% and 45.3% to predict acidemia. Pearson correlation coefficients for T/QRS ratio versus oxygen content and pH were 0.169 and 0.192, respectively.

CONCLUSIONS

(1) In fetal lambs the T/QRS ratio failed to predict hypoxemia or acidemia. (2) Fetal survival was not correlated with the height of the T/QRS ratio during or after asphyxia.

Umbilical cord blood gas analysis at delivery: a time for quality data

OBJECTIVES

To address the practical problems of routine umbilical cord blood sampling, to determine the ranges for pH, PCO2 and base deficit and to examine the relationships of these parameters between cord vessels.

DESIGN

An observational study of umbilical cord artery and vein blood gas results.

SETTING

A large district general hospital in the UK.

SUBJECTS

One thousand nine hundred and forty-two cord results from 2013 consecutive pregnancies of 34 weeks or more gestation, monitored by fetal scalp electrode during labour.

RESULTS

Only 1448 (74.6%) of the 1942 supposedly paired samples had validated pH and PCO2 data both from an artery and the vein; 54 (2.8%) had only one blood sample available, 90 (4.6%) had an error in the pH or PCO2 of one vessel and in 350 (18%) pairs the differences between vessels indicated that they were not sampled from artery and vein as intended. Only 60% of the cases with an arterial pH less than 7.05 had evidence of a metabolic acidosis (base deficit in the extracellular fluid 10 mmol/l or more). Of all the cases, 2.5% had a venous-arterial pH difference greater than 0.22 units.

CONCLUSIONS

Both artery and vein cord samples must be taken and the results screened to ensure separate vessels have been sampled. Interpretation of the results requires the examination of PCO2 and base deficit of the extracellular fluid from each vessel as well as the pH. Confusion about the value of cord gas measurements may be due to the use of erroneous data and inadequate definitions of acidosis which do not differentiate between respiratory and metabolic components.

Prediction of perinatal morbidity at term in small fetuses: comparison of fetal growth and Doppler ultrasound

OBJECTIVE

To compare fetal growth assessed by ultrasound (change in standard deviation score of abdominal circumference and estimated fetal weight) during the third trimester with predelivery ultrasound measurements of fetal size and Doppler measurements from the umbilical and fetal arteries in order to predict suboptimal perinatal outcome in small babies at term.

DESIGN

Prospective observational study.

SETTING

Day assessment unit in a university hospital.

SUBJECTS

One hundred and four consecutive women with a clinical suspicion of a small fetus during the third trimester confirmed by ultrasound (abdominal circumference below the 10th centile) and ultimately delivered at term.

MAIN OUTCOME MEASURES

Acidaemia at birth, fetal distress requiring emergency caesarean section in labour, admission to the neonatal intensive care unit.

RESULTS

Ninety-four babies (90%) weighed less than the 10th centile and the incidence of suboptimal perinatal outcome was 27%. The largest areas under the receiver operating characteristic curves for suboptimal perinatal outcome were obtained with the change in standard deviation score of abdominal circumference and estimated fetal weight, and the ratios of aortic/middle cerebral and renal/middle cerebral pulsatility index. Although low, the odds ratios of the change in estimated fetal weight standard deviation score and the Doppler ratios were significantly different from zero.

CONCLUSION

Ultrasound assessment of fetal growth and predelivery fetal Doppler pulsatility index ratios were superior to predelivery estimates of fetal size and umbilical artery pulsatility index in predicting suboptimal perinatal outcome in small fetuses delivering at term, although the clinical value of such a prediction may be limited.

Indications for operative termination of labor on cardiotocography and fetal blood analysis: the reliability of these methods

In a retrospective study it was possible to show that of 110 cases with operative delivery, performed due to suspicious or pathological fetal blood acidity findings, 93.6% were justified. A pre-pathological or pathological umbilical cord artery pH of < 7.25 was taken as the basis for correct clinical management ("true" positive cases). There was a clear relationship between the pH of the umbilical artery blood and the clinical state of depression in the newborn. This study shows that, with the help of combined fetal supervision using cardiotocography (CTG) as a screening method and fetal blood analysis (FBA) as a method of differentiation, early stages of threatened fetal acidosis can be reliably detected without having too high a rate of operative deliveries, which must inevitably result when continuous CTG supervision is used on its own. Obstetricians should therefore try to prevent severe acidosis combined with a corresponding clinical state of depression of the newborn. This requires the use of modern monitoring (CTG and FBA) and prompt clinical measures (tocolysis or termination of labor) when the pH levels are reduced or are apparently falling.

Clinical evaluation of the fetus and neonate. Relation between intra-partum cardiotocography, Apgar score, cord blood acid-base status and neonatal morbidity

The relation between intra-partum cardiotocography (CTG), cord blood acid-base status, Apgar score and neonatal morbidity was studied in 1228 consecutively live-born babies and in a subgroup of 200 babies (148 babies with a 1 min Apgar score < or = 8 and 52 randomly selected babies with a 1 min Apgar score > or = 9). The scores for the individual components of the 1 min Apgar score were strongly associated with each other, whereas the scores for the individual components of the 5 min Apgar score were less strongly associated. At 1 min the scores for muscle tone, reflex irritability and respiration but not the scores for heart rate and skin colour were associated with arterial and venous cord blood pH (low scores being associated with low pH). Out of the individual components of the Apgar score, heart rate and reflex irritability at 1 min were the best discriminators between "healthy or relatively healthy" and "severely ill" babies. Intrapartum CTG, total Apgar score and cord blood acid-base status were only weakly related. Venous cord blood pH was the best predictor of the 1 min Apgar score. Intra-partum CTG (silent pattern), 5 min Apgar score and venous cord blood pH were the best predictors of severe neonatal morbidity.

ECG waveform analysis in intrapartum fetal monitoring

Intrapartum cardiotocography (CTG) has a high false positive rate and, in the absence of facilities for fetal scalp blood sampling, is associated with increased operative deliveries for 'fetal distress'. It is presently possible to obtain a representative fetal ECG signal using the fetal scalp electrode. There is renewed interest in fetal ECG waveform analysis in the hope that it will improve the specificity of detecting intrapartum fetal hypoxia when there is an abnormal fetal heart rate pattern. Two portions of the fetal ECG are potentially useful: the ST waveform (T/QRS ratio) and the PR interval correlated with the RR interval. Animal experiments suggest that changes in the ST waveform, increase in the T wave amplitude in particular, reflect myocardial anaerobic metabolism. Clinical studies have shown poor correlation between the T wave changes and fetal heart rate changes. There is also concern that the sensitivity of the ST waveform changes for fetal acidaemia may be poor. More information is required before its use is incorporated into routine clinical practice.

Change in electrocardiogram T-wave amplitude during umbilical cord compression is predictive of fetal condition in sheep

OBJECTIVE

The purpose of this study is to assess the usefulness of the dynamic change in T/QRS ratio in fetal electrocardiograms in predicting the fetal condition when repetitive variable decelerations are seen in intrapartum cardiotocograms.

STUDY DESIGN

We investigated the relationship, using linear regression and Wilcoxon's test, between T/QRS and blood gas values, catecholamine concentrations, and blood pressure during repetitive cord compression in five chronically instrumented lamb fetuses.

RESULTS

T/QRS during cord compression correlated significantly (p less than 0.01) with fetal arterial pH (r = -0.7711), norepinephrine concentration (r = 0.7551), and duration of elevated blood pressure during compression (r = -0.8619). Fetal arterial pH and base excess were lower, the duration of elevated blood pressure during compression was shorter, and carbon dioxide partial pressure and catecholamine concentrations were higher in the stage with higher (greater than 0.50) T/QRS during compression (p less than 0.005).

CONCLUSION

We can estimate the severity of fetal distress by measuring T/QRS near the bottom of the decelerations.

Fetal acidosis in labour: a prospective study on the effect of parity

The effect of parity on intrapartum fetal scalp pH was investigated in 6466 patients in labour with a live fetus who were delivered in 1987. 350 (5.4%) required fetal scalp blood sampling for pH (FBS), 236 primigravidae (10.4%) and 114 multigravidae (2.7%) (P less than 0.001). Fetal acidosis (pH less than 7.20) was detected in 35 patients, 27 primigravidae (11.4%) and 8 multigravidae (7.0%) (P less than 0.001). The incidence of intrapartum acidosis in the 2275 primigravidae and the 4191 multigravidae was 1.2 and 0.2% respectively (P less than 0.001). The two deaths from birth asphyxia and three cases of neonatal seizures occurred in primigravidae. In primigravidae requiring FBS, fetal acidosis was not associated with the use of oxytocin or with increased duration of labour. Neonatal seizures were more common overall in primigravidae than in multigravidae and more common in patients requiring FBS than in those not requiring FBS (P less than 0.05). The higher incidence of FBS, fetal scalp acidosis and neonatal seizures in primigravidae has important implications for intrapartum fetal monitoring.

Comparison of the T/QRS ratio of the fetal electrocardiogram and the fetal heart rate during labour and the relation of these variables to condition at delivery

The T/QRS ratio of the fetal electrocardiogram (ECG) was recorded to within 30 min of delivery from 105 women in labour. There were no significant differences in the mean T/QRS ratio in the last hour of record between those with normal and intermediate, or abnormal fetal heart rate (FHR) patterns. In 66 labours the mean T/QRS ratio in the first hour of record was compared with that of the last hour; the only significant change was a small decrease in the mean ratio from 11% to 7% in a group of 11 fetuses with an abnormal FHR pattern throughout the recording time. Eight babies were born with evidence of acidosis (umbilical artery pH less than or equal to 7.16), and another four were born in poor condition (1 min Apgar score less than 4) without evidence of acidosis; none had a mean last hour T/QRS ratio significantly different from the previously established normal range.

Critical analysis of the validity of electronic fetal monitoring

The validity of the diagnosis fetal distress based on electronic fetal monitoring (EFM) is low. It can be argued that the prediction of fetal distress may be influenced by the obstetric intervention, and a number of false-positive (FP) decisions are in fact cases of successful prevention of acidosis. The false-negative decisions (FN) may include cases in which an operative delivery was not performed, although the impaired fetal condition was correctly recognized. To estimated the magnitude of these effects, deliveries after 28 weeks of gestation, in which EFM was applied, were studied. The medical staff involved in these deliveries was asked to estimate the umbilical artery pH immediately before birth. After birth the pH was measured. Cases were classified as operative delivery for fetal distress or other. Fetal distress was supposes to be confirmed if the umbilical artery pH was less than or equal to 7.14. Pre-birth estimates of the pH were obtained in 393 cases. Of the 20 FP cases, 70% were real FP after considering the prebirth estimate; of the 35 FN cases, 89% were real FN. After correction for mistaken false results the sensitivity increased from 20.5% to 29.5% and the predictive value from 31.0% to 51.7%. Although validity and predictive values improve after correcting for the mistaken false results, their values are still unsatisfactorily low.

The diagnostic efficacy of the umbilical arterial systolic/diastolic ratio as a screening tool: a prospective blinded study

This prospective blinded study investigated the diagnostic efficacy of the umbilical arterial systolic/diastolic ratio performed at 34 to 36 weeks' gestation for identifying pregnancies at a high risk for adverse perinatal outcomes. A series of 350 consecutive singleton pregnancies were included in the study. A continuous-wave Doppler instrument with a 4 MHz transducer was used. The criteria for an abnormal perinatal outcome included intrauterine growth retardation, an Apgar score of less than 7 at 5 minutes, umbilical arterial pH at birth less than 7.20, presence of thick meconium, fetal distress in labor, and neonatal complications necessitating admission to the neonatal intensive care nursery. The analytic techniques included determination of the receiver operating characteristic curve, sensitivity, specificity, positive and negative predictive values, and the kappa index. The results demonstrated that although the cutoff value of 2.9 showed the maximum inherent discriminatory power, its diagnostic efficacy (sensitivity, 0.83; specificity, 0.87 positive predictive value, 0.74; negative predictive value, 0.92; and kappa index, 0.68) was not substantially different from that of the more common cutoff value of 3.0 (sensitivity, 0.79; specificity, 0.93; positive predictive value, 0.83; negative predictive value, 0.91; and kappa index, 0.73). Both values were rated good to excellent by the kappa index. The study also demonstrated that the systolic/diastolic ratio was a better predictor of general abnormal outcome than of the suboptimal fetal growth.

Birth asphyxia and the intrapartum cardiotocograph

The intrapartum cardiotocographs (CTGs) of 38 severely asphyxiated, term infants, born during a 17-month period, and those of 120 healthy term infants acting as controls were independently reviewed by three investigators who were unaware of the clinical outcome. Inter-observer agreement was good (Kappa statistic = 0.74, P less than 0.0001). The investigators found that cardiotocographic abnormalities were present in 33 of the asphyxiated infants (87%) and in 35 of the controls (29%) and predicted that the abnormalities were severe enough to lead to significant fetal metabolic acidosis at delivery in 23 asphyxiated infants (61%) and in 11 controls (9%). The differences between the two groups were highly significant (P less than 0.001). Using the traditional diagnostic criteria for fetal distress, the investigators found that fetal blood sampling was indicated in 58% of cases in the asphyxia group and in 20% of controls but was only performed in 16% of asphyxiated infants and in 8% of controls. Furthermore, the median response times of delivery suite staff for abnormal fetal heart rate patterns were similar whether the FHR changes, classified using Krebs' CTG scoring system, were moderate or severe: 80 min and 90 min, respectively. These findings suggest that interpretation of the intrapartum CTG continues to pose major problems for practising obstetricians.

Anaesthesia for emergency caesarean section

The Report on Confidential Enquiries into Maternal Deaths in England and Wales 1982-84 (Department of Health 1989) recommends early involvement of the anaesthetist in women having emergency caesarean sections and the use of epidural anaesthesia in preference to general anaesthesia. In an observational prospective study the need for emergency abdominal delivery could be anticipated in 87% of 360 consecutive emergency caesarean sections. Early establishment of epidural analgesia allowed extension, to an appropriate level for the surgery, in 70%. The duty anaesthetist accompanying the obstetric team on three wardrounds a day could be forewarned of anticipated problems in most women who are eventually delivered abdominally.

Ultrasound Doppler evaluation of uteroplacental and fetoplacental circulation in pre-eclampsia

Blood flow velocity waveforms (FVW) were recorded weekly from the umbilical and arcuate arteries in 58 hospitalised women with a pregnancy complicated by pre-eclampsia. The maximum velocity waveform was analysed for pulsatility index (PI) and the results from the final antenatal examination were related to the outcome of pregnancy. The umbilical artery FVW was abnormal in 36% of the pre-eclamptic pregnancies, as was the arcuate artery FVW in 42%. No difference in FVW was found between mild and severe pre-eclampsia. Abnormal FVW in the umbilical artery was associated significantly both with intra-uterine growth retardation (IUGR) (P less than 0.001) and with signs of fetal distress (FD) (P less than 0.05). Abnormal arcuate artery FVW was associated with FD (P less than 0.05), but not with IUGR. The outcome of pregnancy was related to Placenta Waveform Class, which was derived from the blood velocity on both maternal and fetal sides of placenta. The results suggest that ultrasound Doppler examination of the umbilical artery is a useful aid in monitoring pregnancies complicated by pre-eclampsia, but that arcuate artery examination needs further evaluation.

Fetal ECG during labour: a presentation of a microprocessor system

Changes in the ST waveform of the fetal ECG have been detected in 47 term deliveries with vertex presentations using a specially developed microprocessor-based system for on-line recording of T wave amplitude. The T wave was quantified by the T/QRS ratio. The recording included one scalp electrode for exploration and a maternal skin electrode as reference. Signal quality allowed optimal ST waveform assessment in 89% of the cases. The degree of perinatal asphyxia was judged from cord artery acid-base status and the neonatal outcome. In completely normal fetuses at term the mean T/QRS ratio was 0.148 with a standard deviation of 0.048. With this basic information we can proceed in the investigation of the T/QRS ratio as a means for fetal surveillance.

Ion-selective sensors for assessment of the fetus

Frequent measurement of pH and PCO2 levels of fetal blood during labour provides an insight into the presence and nature of fetal asphyxia, effectiveness of in utero resuscitation and the need for operative delivery. A pH measuring system utilizing a hydrogen ion-selective polymer membrane built into a fetal probe suitable for making intermittent measurements on the fetal scalp during labour is described. Probe design, construction of electrodes and preliminary results obtained using the system in vitro are presented.

Clinical and biochemical assessments of damage due to perinatal asphyxia: a double blind trial of a quantitative method

Using conventional criteria, a series of 26 infants was selected for intrapartum asphyxia from about 4000 deliveries over one year at a single hospital to assess the efficacy of a new biochemical method. Tissue damage was estimated from urinary excretion of hypoxanthine, an important and central intermediate in purine metabolism. The overall pattern showed agreement between the grading (by previously accepted methods) of asphyxia in the perinatal period and our new biochemical approach. The association with handicap at one year of age following asphyxia was complex. This biochemical technique could be used to exclude postasphyxial damage as a cause of clinical disturbances and to select a small group (0.1% of all births) who require further investigation for rarer disorders which may also cause long term handicap.

Umbilical and uteroplacental blood flow velocity waveforms in pregnancies with fetal growth retardation

A 2 MHZ pulsed Doppler ultrasound was used to record blood flow velocity waveforms (FVW) in the umbilical and arcuate arteries of 129 singleton pregnancies where intra-uterine growth retardation (IUGR) was suspected at routine ultrasound screening in the 32nd week of gestation. All patients were examined once a fortnight, between 32nd week and delivery, the results presented being from the final examination before delivery. The FVW were characterized by the pulsatility index (PI). Sixty-six of the 129 newborns were growth-retarded at delivery (birthweight less than or equal to mean--2SD of the general population). Of the IUGR cases, 56% had an abnormal PI (greater than or equal to mean + 2SD of normals) in the umbilical artery and 47% in the arcuate artery. Significant relationships were found between abnormal umbilical artery PI and both IUGR (p less than 0.001) and operative delivery for fetal distress (ODFD) (p less than 0.001). No such relationship was found between abnormal PI in the arcuate artery and either IUGR or ODFD. Four placenta waveform classes (PWC), reflecting the FVW on either side of the placenta, are presented and compared with the outcome of pregnancy. The data show the umbilical artery FVW to be a good predictor of IUGR and intra-uterine fetal distress, whereas the arcuate artery FVW appears to have low predictive value for the above conditions.

Methodology and clinical value of transcutaneous blood gas measurements in the fetus

Aiming at an improvement of fetal surveillance in high risk cases, a clinical trial was performed to evaluate the potential of fetal tcPco2 monitoring. An electrochemical tcPco2 sensor heated at 44 degrees C was applied in 119 fetuses after abnormal heart rate patterns had occurred. The number of operative deliveries for fetal distress was reduced to 14 cases by means of the biochemical parameters (tcPco2) and fetal blood analysis (FBA). In the majority of cases with pathologic heart rate patterns the tcPco2 values were prepathologic or normal (60%), while in 68% of cases with prepathologic heart rate patterns the tcPco2 level was normal. At all instances an intrauterine complication was indicated by a marked rise of the tcPco2 level. The clinical benefit of using the tcPco2 measurement is the better specificity of detecting fetal distress when compared with the use of cardiotocography alone. Furthermore the tcPco2 technique has the advantage of providing continuous information about one biochemical parameter and of avoiding the necessity of repeated incisions of the scalp, as compared with the technique of fetal blood analysis. In conclusion the use of this non-traumatic technique lends itself to avoid unnecessary operative deliveries in high risk cases.