Developmental outcome at 6.5 years after acidosis in term newborns: a population-based study

Use of Photoacoustic Imaging to Study the Effects of Anemia on Placental Oxygen Saturation in Normoxic and Hypoxic Conditions

We aimed to evaluate fetal and placental oxygen saturation (sO2) in anemic and non-anemic pregnant rats throughout gestation using photoacoustic imaging (PAI). Female Sprague-Dawley rats were fed an iron-restricted or iron-replete diet before and during pregnancy. On gestational days 13, 18, and 21, PAI was coupled with high resolution ultrasound to measure oxygenation of the fetus, whole placenta, mesometrial triangle, as well as the maternal and fetal faces of the placenta. PAI was performed in 3D, which allowed sO2 to be measured within an entire region, as well as in 2D, which enabled sO2 measurements in response to a hypoxic event in real time. Both 3D and 2D PAI were performed at varying levels of FiO2 (fraction of inspired oxygen). Iron restriction caused anemia in dams and fetuses, a reduction in fetal body weight, and an increase in placental weight, but overall had minimal effects on sO2. Reductions in FiO2 caused corresponding reductions in sO2 which correlated to the severity of the hypoxic challenge. Regional differences in sO2 were evident within the placenta and between the placenta and fetus. In conclusion, PAI enables non-invasive measurement of sO2 both rapidly and with a high degree of sensitivity. The lack of overt changes in sO2 levels between control and anemic fetuses may suggest reduced oxygen extraction and utilization in the latter group, which could be attributed to compensatory changes in growth and developmental trajectories.

ST waveform analysis vs cardiotocography alone for intrapartum fetal monitoring: An updated systematic review and meta-analysis of randomized trials

INTRODUCTION

ST waveform analysis (STAN) was introduced as an adjunct to cardiotocography (CTG) to improve neonatal and maternal outcomes. The aim of the present study was to quantify the efficacy of STAN vs CTG and assess the quality of the evidence using GRADE.

MATERIAL AND METHODS

We performed systematic literature searches to identify randomized controlled trials and assessed included studies for risk of bias. We performed meta-analyses, calculating pooled risk ratio (RR) or Peto odds ratio (OR). We also performed post hoc trial sequential analyses for selected outcomes to assess the risk of false-positive results and the need for additional studies.

RESULTS

Nine randomized controlled trials including 28 729 women were included in the meta-analysis. There were no differences between the groups in operative deliveries for fetal distress (10.9 vs 11.1%; RR 0.96; 95% confidence interval [CI] 0.82-1.11). STAN was associated with a significantly lower rate of metabolic acidosis (0.45% vs 0.68%; Peto OR 0.66; 95% CI 0.48-0.90). Accordingly, 441 women need to be monitored with STAN instead of CTG alone to prevent one case of metabolic acidosis. Women allocated to STAN had a reduced risk of fetal blood sampling compared with women allocated to conventional CTG monitoring (12.5% vs 19.6%; RR 0.62; 95% CI 0.49-0.80). The quality of the evidence was high to moderate.

CONCLUSIONS

Absolute effects of STAN were minor and the clinical significance of the observed reduction in metabolic acidosis is questioned. There is insufficient evidence to state that STAN as an adjunct to CTG leads to important clinical benefits compared with CTG alone.

Mechanics of vaginal breech birth: Factors influencing obstetric maneuver rate, duration of active second stage of labor, and neonatal outcome

BACKGROUND

We investigated possible parameters that could predict the need for obstetric maneuvers, the duration of the active second stage of labor (i.e., the duration of active pushing), and short-term neonatal outcome in vaginal breech births.

MATERIALS AND METHODS

We performed a retrospective analysis of 268 successful singleton vaginal breech births in women without previous vaginal births from January 2015 to August 2022. Multivariable regression was used to investigate associations between maternal and fetal characteristics (including antepartum magnetic resonance (MR) pelvimetry) with obstetric maneuvers, the duration of active second stage of labor, pH values, and admission to the neonatal unit. Models for the prediction of obstetric maneuvers were built and internally validated.

RESULTS

Obstetric maneuvers were performed in a total of 130 women (48.5%). A total of 32 neonates (11.9%) had to be admitted to the neonatal unit. The intertuberous distance (ITD) (p < 0.001), epidural analgesia (p < 0.001), and birthweight (p = 0.026) were associated with the duration of active second stage of labor. ITD (p = 0.028) and birthweight (p = 0.011) were also independently associated with admission to the neonatal unit, while pH values below 7.10 dropped significantly (p = 0.0034) if ITD was ≥13 cm. Furthermore, ITD (p < 0.001) and biparietal diameter (p = 0.002) were independent predictors for obstetric maneuvers.

CONCLUSIONS

ITD is independently associated with the duration of active second stage of labor. Thus, it can predict suboptimal birth mechanics in the last stage of birth, which may lead to the need for obstetric maneuvers, lower arterial pH values, and admission to the neonatal unit. Consequently, MR pelvimetry gives additional information for practitioners and birthing people preferring a vaginal breech birth.

The effects of inflammation and acidosis on placental blood vessels reactivity

INTRODUCTION

Inflammation and acidosis are two stress stimuli that correspond to pathophysiological processes occurring in placental-mediated vascular disorders. We aimed to investigate the effects of these stimuli on placental chorionic blood vessels reactivity using the ex-vivo placental perfusion model.

METHODS

Term placentas were obtained immediately after cesarean deliveries, and selected cotyledons were cannulated and dually perfused ex-vivo. Placentas were perfused with three different protocols: culture medium (M199-controls, n = 5), culture medium with lipopolysaccharide (inflammatory stimuli) (LPS,1 μg/ml, n = 7), and acidotic culture medium (M - 199, pH: 6.9-7, n = 6). Each perfusion experiment was maintained for 180 min. Fetal perfusion pressure was continuously measured. Measurements in response to angiotensin II (AT II) at the end of the perfusion were compared between the treatment groups, including amplitude of the contraction response, relaxation factor, time to maximal constriction and the area under the pressure curve (AUC).

RESULTS

In response to ATII there was a significant difference in the amplitude of the contraction and the AUC between the treatment groups, (p = 0.049, p = 0.015, respectively). As compared with control perfused cotyledon, the inflammatory stimuli significantly increased the vasoconstriction response to ATII in fetal placental blood vessels, as expressed by increased AUC - median (IQR): 555 (235-1184) vs. 133 (118-207), respectively, p = 0.017. The time to maximal constriction and the relaxation factor did not differ between the groups.

DISCUSSION

Inflammatory stimuli but not acidosis impact fetal-placental vasculature in response to ATII, suggesting that inflammation can compromise vascular function.

Umbilical cord blood acid-base analysis at birth and long-term neurodevelopmental outcomes in children: a systematic review and meta-analysis

BACKGROUND

Umbilical cord blood acid-base sampling is routinely performed at many hospitals. Recent studies have questioned this practice and the association of acidosis with cerebral palsy.

OBJECTIVE

To investigate the associations between the results of umbilical cord blood acid-base analysis at birth and long-term neurodevelopmental outcomes and mortality in children.

SEARCH STRATEGY

We searched six databases using the search strategy: umbilical cord AND outcomes.

SELECTION CRITERIA

Randomised controlled trials, cohorts and case-control studies from high-income countries that investigated the association between umbilical cord blood analysis and neurodevelopmental outcomes and mortality from 1 year after birth in children born at term.

DATA COLLECTION AND ANALYSIS

We critically assessed the included studies, extracted data and conducted meta-analyses comparing adverse outcomes between children with and without acidosis, and the mean proportions of adverse outcomes. The certainty of evidence was assessed using the Grading of Recommendations, Assessment, Development and Evaluations approach.

MAIN RESULTS

We have very low confidence in the following findings: acidosis was associated with higher cognitive development scores compared with non-acidosis (mean difference 5.18, 95% CI 0.84-9.52; n = two studies). Children with acidosis also showed a tendency towards higher risk of death (relative risk [RR] 5.72, 95% CI 0.90-36.27; n = four studies) and CP (RR 3.40, 95% CI 0.86-13.39; n = four studies), although this was not statistically significant. The proportion of children with CP was 2.39/1000 across the studies, assessed as high certainty evidence.

CONCLUSION

Due to low certainty of evidence, the associations between umbilical cord blood gas analysis at delivery and long-term neurodevelopmental outcomes in children remains unclear.

Umbilical cord pH, blood gases, and lactate at birth: normal values, interpretation, and clinical utility

Normal birth is a eustress reaction, a beneficial hedonic stress with extremely high catecholamines that protects us from intrauterine hypoxia and assists in the rapid shift to extrauterine life. Occasionally the cellular O₂ requirement becomes critical and an O₂ deficit in blood (hypoxemia) may evolve to a tissue deficit (hypoxia) and finally a risk of organ damage (asphyxia). An increase in H⁺ concentration is reflected in a decrease in pH, which together with increased base deficit is a proxy for the level of fetal O₂ deficit. Base deficit (or its negative value, base excess) was introduced to reflect the metabolic component of a low pH and to distinguish from the respiratory cause of a low pH, which is a high CO₂ concentration. Base deficit is a theoretical estimate and not a measured parameter, calculated by the blood gas analyzer from values of pH, the partial pressure of CO₂, and hemoglobin. Different brands of analyzers use different calculation equations, and base deficit values can thus differ by multiples. This could influence the diagnosis of metabolic acidosis, which is commonly defined as a pH <7.00 combined with a base deficit ≥12.0 mmol/L in umbilical cord arterial blood. Base deficit can be calculated as base deficit in blood (or actual base deficit) or base deficit in extracellular fluid (or standard base deficit). The extracellular fluid compartment represents the blood volume diluted with the interstitial fluid. Base deficit in extracellular fluid is advocated for fetal blood because a high partial pressure of CO₂ (hypercapnia) is common in newborns without concomitant hypoxia, and hypercapnia has a strong influence on the pH value, then termed respiratory acidosis. An increase in partial pressure of CO₂ causes less increase in base deficit in extracellular fluid than in base deficit in blood, thus base deficit in extracellular fluid better represents the metabolic component of acidosis. The different types of base deficit for defining metabolic acidosis in cord blood have unfortunately not been noticed by many obstetrical experts and organizations. In addition to an increase in H⁺ concentration, the lactate production is accelerated during hypoxia and anaerobic metabolism. There is no global consensus on definitions of normal cord blood gases and lactate, and different cutoff values for abnormality are used. At a pH <7.20, 7% to 9% of newborns are deemed academic; at <7.10, 1% to 3%; and at <7.00, 0.26% to 1.3%. From numerous studies of different eras and sizes, it can firmly be concluded that in the cord artery, the statistically defined lower pH limit (mean -2 standard deviations) is 7.10. Given that the pH for optimal enzyme activity differs between different cell types and organs, it seems difficult to establish a general biologically critical pH limit. The blood gases and lactate in cord blood change with the progression of pregnancy toward a mixed metabolic and respiratory acidemia because of increased metabolism and CO₂ production in the growing fetus. Gestational age-adjusted normal reference values have accordingly been published for pH and lactate, and they associate with Apgar score slightly better than stationary cutoffs, but they are not widely used in clinical practice. On the basis of good-quality data, it is reasonable to set a cord artery lactate cutoff (mean +2 standard deviations) at 10 mmol/L at 39 to 40 weeks' gestation. For base deficit, it is not possible to establish statistically defined reference values because base deficit is calculated with different equations, and there is no consensus on which to use. Arterial cord blood represents the fetus better than venous blood, and samples from both vessels are needed to validate the arterial origin. A venoarterial pH gradient of <0.02 is commonly used to differentiate arterial from venous samples. Reference values for pH in cord venous blood have been determined, but venous blood comes from the placenta after clearance of a surplus of arterial CO₂, and base deficit in venous blood then overestimates the metabolic component of fetal acidosis. The ambition to increase neonatal hemoglobin and iron depots by delaying cord clamping after birth results in falsely acidic blood gas and lactate values if the blood sampling is also delayed. Within seconds after birth, sour metabolites accumulated in peripheral tissues and organs will flood into the central circulation and further to the cord arteries when the newborn starts to breathe, move, and cry. This influence of "hidden acidosis" can be avoided by needle puncture of unclamped cord vessels and blood collection immediately after birth. Because of a continuing anaerobic glycolysis in the collected blood, it should be analyzed within 5 minutes to not result in a falsely high lactate value. If the syringe is placed in ice slurry, the time limit is 20 minutes. For pH, it is reasonable to wait no longer than 15 minutes if not in ice. Routine analyses of cord blood gases enable perinatal audits to gain the wisdom of hindsight, to maintain quality assurance at a maternity unit over years by following the rate of neonatal acidosis, to compare results between hospitals on regional or national bases, and to obtain an objective outcome measure in clinical research. Given that the intrapartum cardiotocogram is an uncertain proxy for fetal hypoxia, and there is no strong correlation between pathologic cardiotocograms and fetal acidosis, a cord artery pH may help rather than hurt a staff person subjected to a malpractice suit based on undesirable cardiotocogram patterns. Contrary to common beliefs and assumptions, up to 90% of cases of cerebral palsy do not originate from intrapartum events. Future research will elucidate whether cell injury markers with point-of-care analysis will become valuable in improving the dating of perinatal injuries and differentiating hypoxic from nonhypoxic injuries.

Associations between fetal heart rate variability and umbilical cord occlusions-induced neural injury: An experimental study in a fetal sheep model

INTRODUCTION

This study evaluated the association between fetal heart rate variability (HRV) and the occurrence of hypoxic-ischemic encephalopathy in a fetal sheep model.

MATERIAL AND METHODS

The experimental protocol created a hypoxic condition with repeated cord occlusions in three phases (A, B, C) to achieve acidosis to pH <7.00. Hemodynamic, gasometric and HRV parameters were analyzed during the protocol, and the fetal brain, brainstem and spinal cord were assessed histopathologically 48 h later. Associations between the various parameters and neural injury were compared between phases A, B and C using Spearman's rho test.

RESULTS

Acute anoxic-ischemic brain lesions in all regions was present in 7/9 fetuses, and specific neural injury was observed in 3/9 fetuses. The number of brainstem lesions correlated significantly and inversely with the HRV fetal stress index (r = -0.784; p = 0.021) in phase C and with HRV long-term variability (r = -0.677; p = 0.045) and short-term variability (r = -0.837; p = 0.005) in phase B. The number of neurological lesions did not correlate significantly with other markers of HRV.

CONCLUSIONS

Neural injury caused by severe hypoxia was associated with HRV changes; in particular, brainstem damage was associated with changes in fetal-specific HRV markers.

Heart rate markers for prediction of fetal acidosis in an experimental study on fetal sheep

To overcome the difficulties in interpreting fetal heart rate (FHR), several tools based on the autonomic nervous system and heart rate variability (HRV) have been developed. The objective of this study was to use FHR and HRV parameters for the prediction of fetal hypoxia. It was an experimental study in the instrumented fetal sheep. Repeated umbilical cord occlusions were performed to achieve severe acidosis. Hemodynamic parameters, ECG, and blood gases were analyzed. The variables used were heart rate baseline, HRV analysis (RMSSD, SDNN, LF, HF, HFnu, Fetal Stress Index (FSI), …), and morphological analysis of decelerations. The gold standard used to classify hypoxia was the fetal arterial pH (pH < 7.10). Different multivariable statistical methods (logistic regression and decision trees) were applied for the detection of acidosis. 21 lambs were instrumented. A total of 130 pairs of FHR/fetal pH analysis were obtained of which 29 in the acidosis group and 101 in the non-acidosis group. After logistic regression model with bootstrap resampling and stepwise backward selection, only one variable was selected, FSI. The AUC of FSI alone in this model was 0.81 with a sensitivity of 0.66, specificity of 0.88, PPV of 0.61, and NPV of 0.90 considering a threshold of 68. Decision trees with CHAID and CART algorithms showed a sensitivity of 0.48 and 0.59, respectively, and a specificity of 0.94 for both. All employed methods identified HRV variables as the most predictive of acidosis. The primary variables selected automatically were those from the HRV. Supporting the use of FHRV measures for the screening of fetal acidosis during labour is interesting.

Proposed cutoff for fetal scalp blood lactate in intrapartum fetal surveillance based on neonatal outcomes: a large prospective observational study

OBJECTIVE

Determination of lactate in fetal scalp blood (FBS) during labour has been recognised since the 1970s. The internationally accepted cutoff of >4.8 mmol/l indicating fetal acidosis is exclusive for the point-of-care device (POC) LactatePro™, which is no longer in production. The aim of this study was to establish a new cutoff for scalp lactate based on neonatal outcomes with the use of the StatstripLactate^® /StatstripXpress^® Lactate system, the only POC designed for hospital use.

DESIGN

Observational study.

SETTING

January 2016 to March 2020 labouring women with indication for FBS were prospectively included from seven Swedish and one Australian delivery unit.

POPULATION

Inclusion criteria: singleton pregnancy, vertex presentation, ≥35⁺⁰  weeks of gestation.

METHOD

Based on the optimal correlation between FBS lactate and cord pH/lactate, only cases with ≤25 minutes from FBS to delivery were included in the final calculations.

MAIN OUTCOME MEASURES

Metabolic acidosis in cord blood defined as pH <7.05 plus BD_ecf >10 mmol/l and/or lactate >10 mmol/l.

RESULTS

A total of 3334 women were enrolled of whom 799 were delivered within 25 minutes. The areas under the receiver operating characteristics curves (AUC) and corresponding optimal cutoff values were as follows; metabolic acidosis AUC 0.87 (95% CI 0.77-0.97), cutoff 5.7 mmol/l; pH <7.0 AUC 0.83 (95% CI 0.68-0.97), cutoff 4.6 mmol/l; pH <7.05 plus BD_ecf ≥12 mmol/l AUC 0.97 (95% CI 0.92-1), cutoff 5.8 mmol/l; Apgar score <7 at 5 minutes AUC 0.74 (95% CI 0.63-0.86), cutoff 5.2 mmol/l; and pH <7.10 plus composite neonatal outcome AUC 0.76 (95% CI 0.67-0.85), cutoff 4.8 mmol/l.

CONCLUSION

A scalp lactate level <5.2 mmol/l using the StatstripLactate^® /StatstripXpress^® system will safely rule out fetal metabolic acidosis.

TWEETABLE ABSTRACT

Scalp blood lactate <5.2 mmol/l using the StatstripLactate^® /StatstripXpress system has an excellent ability to rule out fetal acidosis.

Neurodevelopmental outcome at 24 months of healthy infants at birth with an umbilical artery blood pH ≤ 7 and/or hyperlactacidemia ≥ 7 mmol/L

OBJECTIVE

The incidence of acidosis in term and healthy newborns and the consequences for their neurodevelopment are poorly understood. The aim of our study was to assess neurodevelopmental outcomes at 24 months of age via a parental questionnaire (ASQ, Ages and Stages Questionnaires) for a sample of infants born at term with an umbilical arterial blood pH ≤ 7 or/and hyperlactacidemia ≥ 7 mmol/L. In addition, we compared these groups' neurodevelopmental outcomes with a control group.

METHODS

During the 29 months of the study, we retrospectively included all children who had an umbilical artery (UA) cord blood pH ≤ 7 and/or lactates ≥ 7 mmol/L with good clinical adaptation. We also included a control group of term newborns with normal gases at birth. Ages and Stages questionnaires were sent to parents at 24 months of age.

RESULTS

Among the 9016 births during the study, 7.1% of babies had a UA pH ≤ 7 and/or lactates ≥ 7 mmol/L. The ASQ was considered non-optimal for 32.2% and 36.3% of respondents in the acidosis and control group, respectively, without any significant difference (P = 0.382). After matching for gestational age and sex, there was also no significant difference in the rate of non-optimal ASQ. The percentage of abnormal communication was significantly higher in the control group (19.7% vs 11.4%, P = 0.015).

CONCLUSIONS

Isolated biochemical umbilical cord blood abnormalities in term or near-term newborns with good adaptation do not appear to have a long-term impact on development. These results are rather reassuring, and the absence of specific follow-up for these children seems reasonable.

[Critical Outcome and Hypoxic Ischemic Encephalopathy - A quality Assurance Issue]

The study evaluates the predictive value of the critical status of a newborn as to the risk of developing hypoxic ischemic encephalopathy (HIE).

METHODS

On the basis of the data set from the perinatal survey in Hesse, Germany, in the year 2016, including 52,122 live births (singleton, 37+0 GA), cases of critical newborns were identified. A conjoined analysis with the data set of the neonatal survey from the identical period provided the basis to evaluate the relationship to cases compromised by HIE.

RESULTS

The incidence of cases with a critical outcome (n=11) and those with HIE (n=29) was low. The sensitivity of the status of the newborn for detecting a risk of HIE was 10.34%. The specificity was 99.98%. The positive predictive value was 27.35%. The negative predictive value was 99.95%. The detailed, confidential single-case analysis indicated the ability to avoid negative outcomes in about one third of cases with a critical status of the newborn (4/11) and HIE (9/29).

DISCUSSION AND CONCLUSION

The likelihood of developing encephalopathy (HIE) increases after a critical outcome after birth. Intensified monitoring of these newborns is justified. A single-case analysis identifies the potential ways to improve perinatal outcomes. Measures of external quality assurance should integrate the analysis of both perinatal and neonatal surveys as a basis for quality management (QM).

Umbilical cord arterial and venous gases, ionogram, and glucose level for predicting neonatal morbidity at term

OBJECTIVE

To determine which parameter of umbilical arterial cord gas analysis, pH, base deficit, lactate concentration, ionogram values, or glucose level index is the best predictor of neonatal morbidity at term.

DESIGN

We conducted a 15-month retrospective cohort study that included all nonanomalous, singleton, term births at a single center. The predictive ability of lactate concentration, base deficit, pH, ionogram values, and glucose level were compared using receiver-operating characteristic curves for global and neurological composite morbidity. Optimal cutoff values for lactate concentration, base deficit, and pH were estimated based on their maximum area under the curve.

RESULTS

We included 5161 newborns: 52 (1.01 %) had global composite morbidity, and 17 had (0.33 %) neurological composite morbidity. Blood levels of potassium, calcium, natremia, glucose level, and HCO₃^- did not differ significantly between groups. pH, partial pressure of CO₂, partial pressure of O₂, base deficit, and lactate levels differed significantly between neonates in the groups with and without global composite morbidity. Nearly similar results were found for neurological composite morbidity. The predictive ability did not differ between arterial pH and arterial lactate concentration (P = .25) and base deficit (P = .79). Optimal cutoff values to predict global composite morbidity were arterial pH 7.144, venous pH 7.236, and arterial lactate concentration 6.5 mmol/L.

CONCLUSIONS

Acid-base status analysis remains the best objective indicator for predicting neonatal morbidity and can be estimated using pH, lactate, or base deficit. Ionogram cord blood composition and glucose level do not appear to be useful for this purpose.

Fetal electrocardiography ST-segment analysis for intrapartum monitoring: a critical appraisal of conflicting evidence and a way forward

BACKGROUND

In the past century, some areas of obstetric including intrapartum care have been slow to benefit from the dramatic advances in technology and medical care. Although fetal heart rate monitoring (cardiotocography) became available a half century ago, its interpretation often differs between institutions and countries, its diagnostic accuracy needs improvement, and a technology to help reduce the unnecessary obstetric interventions that have accompanied the cardiotocography is urgently needed.

STUDY DESIGN

During the second half of the 20th century, key findings in animal experiments captured the close relationship between myocardial glycogenolysis, myocardial workload, and ST changes, thus demonstrating that ST waveform analysis of the fetal electrocardiogram can provide information on oxygenation of the fetal myocardium and establishing the physiological basis for the use of electrocardiogram in intrapartum fetal surveillance.

RESULTS

Six randomized controlled trials, 10 meta-analyses, and more than 20 observational studies have evaluated the technology developed based on this principle. Nonetheless, despite this intensive assessment, differences in study protocols, inclusion criteria, enrollment rates, clinical guidelines, use of fetal blood sampling, and definitions of key outcome parameters, as well as inconsistencies in randomized controlled trial data handling and statistical methodology, have made this voluminous evidence difficult to interpret. Enormous resources spent on randomized controlled trials have failed to guarantee the generalizability of their results to other settings or their ability to reflect everyday clinical practice.

CONCLUSION

The latest meta-analysis used revised data from primary randomized controlled trials and data from the largest randomized controlled trials from the United States to demonstrate a significant reduction of metabolic acidosis rates by 36% (odds ratio, 0.64; 95% confidence interval, 0.46-0.88) and operative vaginal delivery rates by 8% (relative risk, 0.92; 95% confidence interval, 0.86-0.99), compared with cardiotocography alone.

Umbilical artery pH and base excess at birth are poor predictors of neurodevelopmental morbidity in early childhood

AIM

We sought to evaluate the associations between umbilical artery pH and base excess and neurodevelopmental outcome at four years of age.

METHODS

This study comprised 84 588 singleton children born alive at term in 2005-2011 in the hospital district of Helsinki and Uusimaa in Finland. Data from the maternity hospital information system were linked to the data from the Medical Birth Register and the Hospital Discharge Register. Neurodevelopmental morbidity included cerebral palsy, epilepsy, intellectual or sensorineural impairment.

RESULTS

After adjustment for maternal and perinatal factors, a combination of pH <7.00 and base excess <-16.00 was associated with infant death (adjusted odds ratio 19.97; 95% confidence interval 5.38-74.17). Values of pH 7.00-7.10 were associated with cerebral palsy (adjusted odds ratio 2.40; 95% confidence interval 1.05-5.47). A combination of low five-minute Apgar score and umbilical artery base excess <-16.00 showed the highest positive predictive value (9.1%) for neurodevelopmental impairments. When umbilical artery pH <7.00 was included, a positive predictive value of 25.0% was observed for infant mortality.

CONCLUSION

Low umbilical artery pH and base excess at birth were the poor predictors of long-term neurodevelopmental morbidity in an unselected population. However, these parameters might be useful in assessing the risk of infant mortality.

Gestational age-related reference values for Apgar score and umbilical cord arterial and venous pH in preterm and term newborns

INTRODUCTION

Despite much literature on reference values of acid-base status in umbilical cord blood at birth, there are as yet no studies performed to determine gestational age-dependent references in cord venous blood and no studies on preterm acid-base standards. Similarly, the normal reference range of Apgar scores for term and preterm infants has not yet been determined.

MATERIAL AND METHODS

Data were obtained from the maternity units of Skåne University Hospital, Malmö and Lund, Sweden, from 2001 to 2010. Validated paired arterial and venous cord pH values were obtained from 27 175 newborns, of whom 18 584 had spontaneous, non-instrumental vaginal deliveries and a 5-minute Apgar score equal to or greater than the median value for the individual gestational week. Simple linear and polynomial regression analyses were performed. Values were reported as mean ± standard deviation and median with 2.5th and 97.5th percentiles.

RESULTS

Median 5-minute Apgar score was 7 for gestations shorter than 28 weeks, 8 for 28 weeks, 9 for 29-30 weeks, and 10 from 31 weeks onwards. A linear decline in pH for both cord arterial and venous blood was seen with advancing gestational age (P < 0.001).

CONCLUSIONS

Median 5-minute Apgar scores were <10 before 31 weeks of gestation. Both umbilical cord arterial and venous pH decreased linearly with increasing gestational age. Further studies are needed to show whether gestational age-related pH reference ranges might be preferred to fixed cut-offs in the estimation of umbilical cord acidemia at birth.

Boys and girls differ in symptoms and neurodevelopmental outcome after perinatal metabolic acidosis, a population-based study

AIM

To evaluate sex differences in infants born at term with metabolic acidosis with regard to perinatal health and symptomatology, and developmental outcome.

METHODS

From a population-based cohort of infants born at term (n = 14 687), 78 were prospectively identified as having metabolic acidosis at birth. Two matched controls per case were selected. Sex differences in perinatal characteristics and in neurodevelopmental outcome at 6.5 years of age were analysed. Subgroup analysis was made based on need of neonatal care and planned follow-up.

RESULTS

Acidotic boys who appeared healthy, that is with no need of specialised neonatal care respectively only followed at ordinary health care service, have worse perinatal symptoms and less favourable neurodevelopmental outcome compared to girls. The male disadvantage concerning neurodevelopmental outcome was also indicated in children without acidosis. Outcome at 6.5 years was associated with Apgar at 10 minutes (p = 0.03), need of neonatal care (p = 0.04) and sex (p = 0.02) but not acidosis per se (p = 0.54).

CONCLUSION

Sex affected immediate symptomatology in term acidotic infants and neurodevelopmental outcome at the age of 6.5 years. The findings were seen in those who appeared healthy in the neonatal period. The results suggest that sex should be considered in assessment of acidotic children.

Population-based reference curve for umbilical cord arterial pH in infants born at 28 to 42 weeks

OBJECTIVE

The objective of the study was to examine normal variations of umbilical cord arterial pH by gestational age (GA).

STUDY DESIGN

Population-based cohort study of 46 199 infants born from 2008 to 2014 in Stockholm, Sweden, with GA 28 to 42 weeks, Apgar score ⩾7 at 5 min, non-instrumental vaginal delivery, and birth weight for GA⩾3rd and ⩽97th percentile. Quantile regression was used to investigate the associations between GA and infant sex, and pH.

RESULTS

The mean umbilical cord arterial pH (s.d.) was 7.29 (0.10), 7.27 (0.07), 7.25 (0.07) and 7.23 (0.07) among infants born at 28 to 31, 32 to 36, 37 to 41 and 42 weeks, respectively. Arterial pH decreased linearly with increasing GA, and female infants had higher pH than male infants (P<0.001).

CONCLUSION

Umbilical cord arterial pH varied in a linear fashion by GA and was influenced by infant sex. The provided reference curve taking GA into account may yield a more accurate definition of acidosis at birth.

Umbilical lactate as a measure of acidosis and predictor of neonatal risk: a systematic review

BACKGROUND

Umbilical cord lactate is one approach to measuring acidosis and intrapartum hypoxia, knowledge of which may be helpful for clinicians involved in the care of women and newborns.

OBJECTIVE

To synthesise the evidence on accuracy of umbilical cord lactate in measuring acidosis and predicting poor neonatal outcome.

SEARCH STRATEGY

Studies published and unpublished between 1990 and 2014 from PubMed/Medline, EMBASE, Cochrane Central Register of Controlled Trials, and clinicaltrials.gov were assessed.

SELECTION CRITERIA

Cross-sectional and randomised studies that assessed fetal acidosis (using lactate as the index test) with or without an assessment of neonatal outcome.

DATA COLLECTION AND ANALYSIS

Correlations between index and reference test(s) were recorded, as were the raw data to classify the predictive ability of umbilical lactate for neonatal outcomes. Meta-analysis of correlation was performed. We plotted estimates of the studies' observed sensitivities and specificities on Forest plots with 95% confidence intervals (CI). Where possible, we combined data using meta-analysis, applying the hierarchical summary receiver operating characteristics model and a bivariate model.

MAIN RESULTS

Twelve studies were included. Umbilical lactate correlated with pH [pooled effect size (ES) -0.650; 95% CI -0.663 to -0.637, P < 0.001], base excess (ES -0.710; 95% CI -0.721 to -0.699, P < 0.001), and Apgar scores at 5 minutes (ES 0.300; 95% 0.193-0.407, P < 0.001). Umbilical lactate had pooled sensitivity and specificity for predicting neonatal neurological outcome including hypoxic ischaemic encephalopathy of 69.7% (95% CI 23.8-94.4%) and 93% (95% CI 86.8-96.3%).

AUTHORS' CONCLUSION

Umbilical cord lactate is a clinically applicable, inexpensive and effective way to measure acidosis and is a tool that may be used in the assessment of neonatal outcome.

TWEETABLE ABSTRACT

Umbilical cord lactate: a clinically applicable, inexpensive, effective way to measure intrapartum acidosis.

Risk factors for emergency caesarean section in planned vaginal breech delivery

PURPOSE

To identify risk factors for emergency caesarean section in women attempting a vaginal breech delivery at term.

METHODS

Data from 1092 breech deliveries performed between 1998 and 2013 at a Swiss cantonal hospital were extracted from an electronic database. Of the 866 women with a singleton, full term pregnancy, 464 planned a vaginal breech delivery. Fifty-seven percent (265/464) were successful in delivering vaginally. Multivariate regression analyses of risk factors were performed, and neonatal and maternal complications were compared.

RESULTS

Risk factors for failed vaginal delivery were peridural anaesthesia (OR 2.05; 95 % CI 1.09-3.84; p = 0.025), nulliparity (OR 2.82; 95 % CI 1.87-4.25; p < 0.001), high birth weight (OR 1.17; 95 % CI 1.04-1.30; p = 0.006) and induction of labour (OR 1.56; 95 % CI 1.003-2.44; p = 0.048). Maternal age, height and weight; gestational age; or newborn length and head circumference were not associated with an unplanned caesarean section. The rate of successful vaginal delivery in the low risk sub-group (multiparous women without induction of labour) was 58-83 %, depending on birth weight category. The likelihood of success for the high risk sub-group (nulliparous women with induction of labour) fell below a third at neonatal birth weights >3250 g. Complication rates were low in the cohort.

CONCLUSIONS

Use of peridural anaesthesia, nulliparity, high birth weight and induction of labour were risk factors for unsuccessful vaginal breech delivery requiring an unplanned caesarean section. Awareness of these risk factors is useful when counselling women who are considering a vaginal breech delivery.

Limitations in the Activity of Mobility at Age 6 Years After Difficult Birth at Term: Prospective Cohort Study

BACKGROUND

A difficult birth at term (DBAT) may manifest as fetal acidosis and low Apgar scores and is often referred to as "perinatal asphyxia," especially when infants show signs of neonatal encephalopathy (NE). In contrast to DBAT resulting in moderate-to-severe NE, which is associated with neurodevelopmental disorders, little is known about the prognosis of less severe forms of DBAT, with or without NE.

OBJECTIVE

The purpose of this study was to evaluate the International Classification of Functioning, Disability and Health, Children & Youth Version activity "mobility" and other neurodevelopmental sequelae in infants with DBAT at age 6 years.

METHODS

The index cohort (n=62; 35 boys, 27 girls) consisted of consecutive term infants with DBAT based on clinical criteria in a Dutch nonacademic hospital from 1999 to 2005. Neonatal encephalopathy was assessed according to the Sarnat grading system and excluded infants with severe NE. The matched reference cohort (n=81; 49 boys, 32 girls) consisted of healthy term infants. The primary outcome at 6 years was limited mobility (Movement Assessment Battery for Children score ≤15th percentile). Secondary outcomes included learning and behavioral problems and the presence of minor neurological dysfunction.

RESULTS

Three children developed cerebral palsy and were excluded from analyses. Children with DBAT more often had limited mobility than children without DBAT (risk ratio [RR]=2.44; 95% confidence interval [95% CI]=1.16, 5.14). The risk of limited mobility rose with increasing severity of NE (mild NE: RR=3.38; 95% CI=1.40, 8.16; moderate NE: RR=4.00; 95% CI=1.54, 10.40), and manual abilities especially were affected (RR=4.12; 95% CI=1.40, 12.14). Learning problems, need for physical therapy, and complex minor neurological dysfunction were more common in children with DBAT than in children without DBAT.

CONCLUSIONS

Term infants who develop mild or moderate NE following DBAT are at increased risk for limited mobility at age 6 years. Routine monitoring of neuromotor development in these children is warranted.

Perinatal inflammation/infection and its association with correction of metabolic acidosis in hypoxic-ischemic encephalopathy

OBJECTIVE

To investigate the decreased response to hypothermia in neonates with hypoxic-ischemic encephalopathy (HIE) and infection, we sought to determine the association of fetal inflammation/infection with perinatal metabolic acidosis.

STUDY DESIGN

We performed a retrospective cohort study of neonates with suspected HIE started on whole-body hypothermia within 6 h of birth that had a cord gas at delivery and placental pathology performed. Neonates were compared based on the presence of clinical and histologic chorioamnionitis. The cord gas at delivery was compared with the initial arterial gas after birth.

RESULTS

In all, 50 out of 67 (74.6%) neonates admitted for therapeutic hypothermia met inclusion criteria. Chorioamnionitis did not affect the cord gas at delivery, but both clinical and histologic chorioamnionitis were associated with a significantly increased metabolic acidosis on the initial neonatal arterial gas.

CONCLUSION

Chorioamnionitis, diagnosed both clinically and histologically, is associated with a persistent state of acidosis in neonates with HIE that may contribute to worse neurologic outcomes.

Metabolic acidosis in the first 14 days of life in infants of gestation less than 26 weeks

Extremely immature newborns develop a self-limiting normal anion gap metabolic acidosis in early life. This study examined the natural history of this acidosis in a population of infants of gestation less than 26 weeks in the first 14 days of life. The acidosis was maximal on day 4 with a mean base deficit of 10.6 mmol/l and had resolved in 90 % of infants by day 11. Dopamine usage was the only independent predictor of the acidosis. Its use was associated with a greater degree of acidosis.

CONCLUSION

Extremely preterm infants experience a self-limiting normal anion gap metabolic acidosis in the first 2 weeks of life which is consistent with renal tubular immaturity.

Association between umbilical cord artery pCO₂ and the Apgar score; elevated levels of pCO₂ may be beneficial for neonatal vitality after moderate acidemia

OBJECTIVE

To determine the association between 5-min Apgar score and umbilical cord artery carbon dioxide tension (pCO₂).

DESIGN

Observational study.

SETTING

European hospital labor wards.

POPULATION

Data from 36,432 newborns ≥36 gestational weeks were obtained from three sources: two trials of monitoring with fetal electrocardiogram (the Swedish randomized controlled trial and the European Union Fetal ECG trial) and Mölndal Hospital data. After validation of the acid-base values, 25,806 5-min Apgar scores were available for analysis.

METHODS

Validation of the umbilical cord acid-base values was performed to obtain reliable data. 5-min Apgar score was regressed against cord artery pCO₂ in a polynomial multilevel model.

MAIN OUTCOME MEASURES

Five-min Apgar score, umbilical cord pCO₂, pH, and base deficit.

RESULTS

Overall, a higher cord artery pCO₂ was found to be associated with lower 5-min Apgar scores. However, among newborns with moderate acidemia, lower umbilical cord artery pCO₂ (≤median pCO₂ for the specific cord artery pH) was associated with lower 5-min Apgar scores, with a relative risk of 2.0 (95% confidence interval: 1.4-2.8) for 5-min Apgar scores 0-6.

CONCLUSIONS

Metabolic acidosis affects the newborn's vitality more than respiratory acidosis. In addition, elevated levels of pCO₂ may be beneficial for fetuses with moderate acidemia, and thus cord artery pCO₂ is a factor that should be considered when assessing the compromised newborn.

Relationship between severe acidemia, verbal abilities, and behavior in a Spanish cohort of 5-year-old children born at term

AIM

To determine whether a relationship exists between the markers of severe acidemia (SA) and the developmental, verbal, and behavioral characteristics of children with SA born at term 5 years previously, without apparent neurological impairment.

METHODS

A cohort of 76 children-38 with SA (pH < 7, base deficit ≥12 mmol/L) and 38 non-SA (pH ≥ 7.20)-were evaluated using the Battelle Developmental Inventory, McCarthy's Verbal Scale, the Token Test for Children, and the Conners 3rd Edition-Parent. The relationships between markers of SA and verbal and behavioral scores were analyzed with parametric correlations. Multiple regression analysis was used to determine the possible effect of these markers on verbal abilities, verbal memory, and attention.

RESULTS

Although none of the scores were in the "impaired" range, the SA group scored lower in verbal index (p = .000) and verbal memory (p = .004) on the McCarthy's Scales and in verbal comprehension (p = .001) on the Token Test for Children-2, and higher on the inattention (p = .003) and hyperactivity-impulsivity domains of the Conners Scales (p = .009) compared with the control group. There were no differences between the groups in the motor, personal-social, or cognitive domains on the Battelle Developmental Inventory. The SA markers were found to be predictors, accounting for 61.6% of verbal variability.

CONCLUSIONS

SA markers reflect mild long-term consequences regarding verbal abilities and inattentiveness among children born at term without apparent neurological impairment on discharge but do not suggest severe impairment to the 5-year development of children. The authors recommend that these children should be monitored to determine whether they need or might benefit from an early intervention program.