Umbilical cord blood acid-base state: what is normal?

Prevention of fetal brain injury in category II tracings

INTRODUCTION

With category II fetal heart rate tracings, the preferred timing of interventions to prevent fetal hypoxic brain damage while limiting operative interventions remains unclear. We aimed to estimate fetal extracellular base deficit (BDecf ) during labor with category II tracings to quantify the timing of potential interventions to prevent severe fetal metabolic acidemia.

MATERIAL AND METHODS

A longitudinal study was conducted using the database of the Recurrence Prevention Committee, Japan Obstetric Compensation System for Cerebral Palsy, including infants with severe cerebral palsy born at ≥34 weeks' gestation between 2009 and 2014. Cases included those presumed to have an intrapartum onset of hypoxic-ischemic insult based on the fetal heart rate pattern evolution from reassuring to an abnormal pattern during delivery, in association with category II tracings marked by recurrent decelerations and an umbilical arterial BDecf  ≥ 12 mEq/L. BDecf changes during labor were estimated based on stages of labor and the frequency/severity of fetal heart rate decelerations using the algorithm of Ross and Gala. The times from the onset of recurrent decelerations to BDecf 8 and 12 mEq/L (Decels-to-BD8, Decels-to-BD12) and to delivery were determined. Cases were divided into two groups (rapid and slow progression) based upon the rate of progression of acidosis from onset of decelerations to BDecf 12 mEq/L, determined by a finite-mixture model.

RESULTS

The median Decels-to-BD8 (28 vs. 144 min, p < 0.01) and Decels-to-BD12 (46 vs. 177 min, p < 0.01) times were significantly shorter in the rapid vs slow progression. In rapid progression cases, physicians' decisions to deliver the fetus occurred at ~BDecf 8 mEq/L, whereas the "decisions" did not occur until BDecf reached 12 mEq/L in slow progression cases.

CONCLUSIONS

Fetal BDecf reached 12 mEq/L within 1 h of recurrent fetal heart rate decelerations in the rapid progression group and within 3 h in the slow progression group. These findings suggest that cases with category II tracings marked by recurrent decelerations (i.e., slow progression) may benefit from operative intervention if persisting for longer than 2 h. In contrast, cases with sudden bradycardia (i.e., rapid progression) represent a challenge to prevent severe acidosis and hypoxic brain injury due to the limited time opportunity for emergent delivery.

Umbilical cord gas analysis: clinical implications of a comprehensive, contemporary determination of normal ranges

BACKGROUND

Umbilical cord gases are often used to assess the impact of labor and delivery on the fetus. However, no large series exists that reflects contemporary obstetrical practice or that analyzed blood gas ranges by route of delivery. Baseline, prelabor acid-base status in the human fetus is also poorly defined, rendering the assessment of blood gas changes during labor difficult.

OBJECTIVE

This study aimed to define normal umbilical cord gas and lactate values, stratified by mode of delivery, in a large contemporary series in which universal umbilical cord gas evaluation was dictated by protocol.

STUDY DESIGN

This was a retrospective cohort study. We analyzed the umbilical cord gas and lactate data of an unselected population of infants born between March 2012 and April 2022 at a large teaching hospital. These values were then analyzed by mode of delivery and, for cesarean deliveries, by indication for cesarean delivery and type of anesthesia. Umbilical cord gas values from infants delivered by elective cesarean delivey under general anesthesia without labor were considered representative of baseline, prelabor values.

RESULTS

Data were available for 45,475 infants. The median arterial pH values and interquartile ranges for vaginal births, elective cesarean deliveries without labor, and cesarean deliveries performed for fetal heart rate concerns were 7.27 (0.09), 7.27 (0.06), and 7.25 (0.09), respectively. Arterial lactate values for these same 3 groups were 4.1 (2.5), 2.5 (1.2), and 4.0 (2.8) mmoles/L, respectively. Because of the very large sample size, most comparisons yielded differences that were statistically significant, but clinically irrelevant. Of all the infants, 14% had an arterial pH <7.20; a pH value of 7.1 represents 2 standard deviations from the mean.

CONCLUSION

This large, population-based study of umbilical cord gas and lactate levels in an unselected population, stratified by delivery mode, represents a previously unavailable benchmark for the evaluation of umbilical cord gases. Arterial umbilical cord pH values for infants delivered by elective caesarean delivery without labor (median pH 7.28) reflect a lower prelabor fetal pH baseline than previously assumed. This finding, coupled with our determination that a 2 standard deviation below normal pH limit of 7.1, instead of the historic arbitrary pH of 7.2 threshold, helps to explain the poor positive predictive value of electronic fetal heart rate monitoring, a test designed to detect arterial pH levels that have fallen from an assumed baseline near pH 7.4 to an assumed potentially injurious pH level of <7.2. Uncomplicated labor, even when prolonged, does not generally lead to a clinically significant cumulative hypoxic stress to the human fetus. These findings, along with our determination that there is no difference in the acid-base status among infants delivered by cesarean delivery for fetal heart rate concerns, help to explain the failure of current approaches in labor and delivery management to reduce the rates of neonatal hypoxic-ischemic encephalopathy and cerebral palsy, conditions that almost always reflect developmental events rather than the effects of labor on the fetus.

Multi-organ dysfunction in infants with acidosis at birth in the absence of moderate to severe hypoxic ischemic encephalopathy

INTRODUCTION

Infants with perinatal asphyxia are at risk for organ failure aside from the brain, regardless of the severity of the asphyxial insult. We aimed to evaluate the presence of organ dysfunction other than the brain in newborns with moderate to severe acidosis at birth, in the absence of moderate to severe hypoxic ischemic encephalopathy.

MATERIALS AND METHODS

Data of 2 years were retrospectively recorded. Late preterm and term infants admitted to the intensive care unit with ph < 7.10 and BE < -12 mmol/l in the first hour were included in the absence of moderate to severe hypoxic ischemic encephalopathy. Respiratory dysfunction, hepatic dysfunction, renal dysfunction, myocardial depression, gastrointestinal problems, hematologic system dysfunction, and circulatory failure were evaluated.

RESULTS

Sixty-five infants were included [39 (37-40) weeks, 3040 (2655-3380) grams]. Fifty-six (86 %) infants had one or more dysfunction in any system [respiratory: 76.9 %, hepatic: 20.0 %, coagulation: 18.5 %, renal: 9.2 %, hematologic: 7.7 %, gastrointestinal: 3.0 %, and cardiac: 3.0 %]. Twenty infants had at least two affected systems. The incidence of coagulation dysfunctions was higher in the infants with severe acidosis (n = 25, ph < 7.00) than the infants with moderate acidosis (n = 40: pH = 7.00-7.10); 32 % vs 10 %; p = 0.03.

CONCLUSIONS

Moderate to severe fetal acidosis is associated with the development of extra-cranial organ dysfunctions in infants who do not require therapeutic hypothermia. A monitoring protocol is needed for infants with mild asphyxia in order to identify and manage potential complications. Coagulation system should be carefully evaluated.

Manually Controlled, Continuous Infusion of Phenylephrine or Norepinephrine for Maintenance of Blood Pressure and Cardiac Output During Spinal Anesthesia for Cesarean Delivery: A Double-Blinded Randomized Study

BACKGROUND

To counteract the vasoplegia induced by spinal anesthesia (SA) and maintain blood pressure (BP) during cesarean delivery, phenylephrine is currently recommended, but norepinephrine might offer superior preservation of cardiac output. We aimed to compare the hemodynamic effects of phenylephrine and norepinephrine administered by manually adjusted continuous infusion during elective cesarean delivery.

METHODS

In this pragmatic, parallel-group, double-blind randomized controlled trial, 124 parturients scheduled for elective cesarean delivery under SA in a tertiary maternity in France, between February 2019 and December 2020, were randomized to receive norepinephrine at a starting rate of 0.05 μg·kg -1 ·min -1 (n = 62) or phenylephrine at a starting rate of 0.5 μg·kg -1 ·min -1 (n = 62). In both groups, the vasopressor infusion rate was then manually adjusted to maintain maternal systolic BP above 90% of the baseline value. The primary outcome, the change in cardiac index (CI) measured by thoracic bioreactance from SA to umbilical cord clamping, was analyzed through repeated measures analysis of variance and post hoc t tests. Secondary outcomes included maternal BP and neonatal outcomes.

RESULTS

In the norepinephrine group, cardiac index was maintained between 90% and 100% of baseline from SA to umbilical cord clamping, whereas it was maintained at significantly lower values (81%-88%) in the phenylephrine group ( P = .001). The percentage of elapsed time with a mean maternal BP <65 mm Hg and with systolic BP <80% of the baseline value was higher in the phenylephrine group: 2.9% (7.3) vs 0.5% (1.8) (absolute risk difference [ARD], -2.4%; 95% confidence interval, -4.4 to -0.5; P = .012) and 8.5% (16.6) vs 2.3% (5.2) (ARD, -6.2%; 95% confidence interval, -10.6 to -1.8; P = .006). Excluding parturients with gestational diabetes, severe neonatal hypoglycemia was more common in the phenylephrine group at 19.6% (9/46) vs 4.1% (2/49) ( P = .02). The other neonatal outcomes did not differ significantly between the groups.

CONCLUSIONS

When administered by manually adjusted infusion during SA for cesarean delivery, norepinephrine was associated with a higher CI; both infusions were effective for maintaining BP.

Umbilical cord blood gases: probability of arterial or venous source in acidemia

OBJECTIVES

Umbilical cord blood gases (UBG) may be a critical element in the assessment of a depressed newborn infant but in some cases the arterial or venous UBG source is uncertain making clinical and/or medical-legal interpretation difficult. Objective: to estimate the probability of an arterial (ProbAS) or venous (ProbVS) UBG source depending on blood gas parameters in acidemic cases.

METHODS

A total of 56,703 pairs of concomitant arterial and venous (CAV) UBG results assayed over an 8.8-year period were analyzed. Specimen pairs with preanalytical issues, duplicate source, or physiologically out-of-range or uninterpretable results were excluded. The 3,579 CAV-UBGs with an arterial and venous pH 6.70 to 7.25 were analyzed. Generalized additive model (gam)-based binomial logistic regressions were used to determine the ProbAS and ProbVS according to the blood gas parameters.

RESULTS

The relative differences between arterial and venous medians were: pO₂ ‒47%, pCO₂ 22%, pH -11%, and BD 4%. Below a median of 2.4 kPa, the lower the pO₂, the higher the ProbAS. Above this value, the higher the pO₂, the lower the ProbAS. An Excel worksheet is provided to calculate ProbAS and ProbVS from the regression model for different combinations of pH, pCO₂, and pO₂ values. Considering ProbAS and ProbVS above a cutoff 0.8, the model correctly identified the source in 56% of cases while 41% were indeterminant and 3% were erroneous.

CONCLUSIONS

The probability of an arterial or venous source of an umbilical blood gas can be estimated based on the pH, pCO₂, and pO₂ in most acidemic specimens.

Identification of the Fetus at Risk for Metabolic Acidemia Using Continuous Fetal Heart Rate Monitoring

The fetal heart rate can be used to assess the current metabolic state of the fetus and predict the risk of the evolution of metabolic acidemia through the course of labor. In this chapter, we will present the pathophysiology of the development of fetal acidemia and provide an organized approach to identifying the risk of worsening acidemia using changes noted in the fetal heart rate pattern to allow for interventions that might alter this course.

Forensic Analysis of Umbilical and Newborn Blood Gas Values for Infants at Risk of Cerebral Palsy

Cerebral palsy litigation cases account for the highest claims involving obstetricians/gynecologists, a specialty that ranks among the highest liability medical professions. Although epidemiologic studies indicate that only a small proportion of cerebral palsy (10-20%) is due to birth asphyxia, negligent obstetrical care is often alleged to be the etiologic factor, resulting in contentious medical-legal conflicts. Defense and plaintiff expert opinions regarding the etiology and timing of injury are often polarized, as there is a lack of established methodology for analysis. The objective results provided by umbilical cord and newborn acid/base and blood gas values and the established association with the incidence of cerebral palsy provide a basis for the forensic assessment of both the mechanism and timing of fetal neurologic injury. Using established physiologic and biochemical principles, a series of case examples demonstrates how an unbiased expert assessment can aid in both conflict resolution and opportunities for clinical education.

Hyperbaric prilocaine vs. hyperbaric bupivacaine for spinal anaesthesia in women undergoing elective caesarean section: a comparative randomised double-blind study

Hyperbaric bupivacaine spinal anaesthesia remains the gold standard for elective caesarean section, but the resultant clinical effects can be unpredictable. Hyperbaric prilocaine induces shorter motor block but has not previously been studied in the obstetric spinal anaesthesia setting. We aimed to compare duration of motor block after spinal anaesthesia with prilocaine or bupivacaine during elective caesarean section. In this prospective randomised, double-blind study, women with uncomplicated pregnancy undergoing elective caesarean section were eligible for inclusion. Exclusion criteria included: patients aged < 18 years; height < 155 cm or > 175 cm; a desire to breastfeed; or a contra-indication to spinal anaesthesia. Patients were randomly allocated to two groups: the prilocaine group underwent spinal anaesthesia with 60 mg intrathecal prilocaine; and the bupivacaine group received 12.5 mg intrathecal heavy bupivacaine. Both 2.5 µg sufentanil and 100 µg morphine were added to the local anaesthetic agent in both groups. The primary outcome was duration of motor block, which was assessed every 15 min after arriving in the post-anaesthetic care unit. Maternal haemodynamics, APGAR scores, pain scores, patient satisfaction and side-effects were recorded. Fifty patients were included, with 25 randomly allocated to each group. Median (IQR [range]) motor block duration was significantly shorter in the prilocaine group, 158 (125-188 [95-249]) vs. 220 (189-250 [89-302]) min, p < 0.001. Median length of stay in the post-anaesthetic care unit was significantly shorter in the prilocaine group, 135 (120-180 [120-230]) vs. 180 (150-195 [120-240]) min, p = 0.009. There was no difference between groups for: maternal intra-operative hypotension; APGAR score; umbilical cord blood pH; maternal postoperative pain; and patients' or obstetricians' satisfaction. We conclude that hyperbaric prilocaine induces a shorter and more reliable motor block than hyperbaric bupivacaine for women with uncomplicated pregnancy undergoing elective caesarean section.

MiRNAs Regulating Oxidative Stress: A Correlation with Doppler Sonography of Uteroplacental Complex and Clinical State Assessments of Newborns in Fetal Growth Restriction

Overproduction of reactive oxygen species (ROS) and, as a result, uncontrolled oxidative stress (OS) can play a central role in disorders of fetal hemodynamics and subsequent development of adverse perinatal outcomes in newborns with fetal growth restriction (FGR). Given the epigenetic nature of such disorders, the aim of our study was to evaluate the expression of miRNAs associated with OS and endothelial dysfunction (miR-27a-3p, miR-30b-5p, miR-125b-5p, miR-221-3p, miR-451a and miR-574-3p) in umbilical cord blood using real-time quantitative RT-PCR. ΜiRNA expression was evaluated in patients with FGR delivery before (n = 9 pregnant) and after 34 weeks of gestation (n = 13 pregnant), and the control groups corresponding to the main groups by gestational age (13 pregnant women in each group, respectively). A significant increase in miR-451a expression was detected in late-onset FGR and correlations with fetoplacental and cerebral circulation were established (increase of resistance in the umbilical artery (pulsatility index, PI UA (umbilical artery): r = −0.59, p = 0.001) and a decrease in cerebral blood flow (CPR: r = 0.48, p = 0.009)). The change in miR-125b-5p expression in the placenta is associated with reduced Doppler of cerebral hemodynamics (CPR: r = 0.73, p = 0.003; PI MCA (middle cerebral artery): r = 0.79, p = 0.0007), and newborn weight (r = 0.56, p = 0.04) in early-onset FGR. In addition, significant changes in miR-125b-5p and miR-451a expression in umbilical cord blood plasma were found in newborns with neonatal respiratory distress syndrome (NRDS) (in early-onset FGR) and very low birth weight (VLBW) (in late-onset FGR). A number of key signaling pathways have been identified in which the regulation of the studied miRNAs is involved, including angiogenesis, neurotrophin signaling pathway and oxidative stress response. In general, our study showed that changes of the redox homeostasis in the mother-placenta-fetus system in FGR and subsequent perinatal outcomes may be due to differential expression of oxidative stress-associated miRNAs.

<p>What is the Impact of Abnormal Amniotic Fluid Volumes on Perinatal Outcomes in Normal Compared with At-Risk Pregnancies?</p>

Objective

Assessing amniotic fluid volume is an integral part of obstetric practice. Data are sparse on at-risk pregnancy and amniotic fluid volumes. The aim of our study was to determine if there is a difference in perinatal outcomes based on complications of pregnancy and amniotic fluid volumes. We hypothesized that at-risk pregnancies with abnormal amniotic fluid volumes would have worse perinatal outcomes than normal pregnancies with abnormal amniotic fluid volumes.

Study Design

This retrospective cohort study evaluated both normal and at-risk singleton pregnancies with intact membranes on admission for delivery. Amniotic fluid volumes were estimated using both the amniotic fluid index (AFI) and single deepest pocket (SDP) techniques. All sonograms were performed by trained ultrasound technicians or obstetrician/gynecologists. We placed 3365 women into 6 separate groups (at-risk versus normal, then further stratified by oligohydramnios by SDP, normal fluid, or polyhydramnios by AFI).

Results

At-risk pregnancies with normal fluid and at-risk pregnancies with polyhydramnios have significantly increased risk of neonatal intensive care unit (NICU) admission [OR 2.06 (95% CI 1.63,2.60), OR 2.74 (95% CI 1.54, 4.87)]. Birthweight is significantly higher in at-risk and normal pregnancies with polyhydramnios than those with normal pregnancies and normal fluid (p<0.0001). Birthweight is significantly lower in at-risk pregnancies with oligohydramnios (p<0.0001). There were no significant differences in need for amnioinfusion in labor, variables or lates influencing delivery, meconium staining, or umbilical artery pH <7.1.

Conclusion

Our study attempted to further define risk of adverse pregnancy outcomes by defining the pregnancy as normal or at-risk and amniotic fluid volumes. Contrary to our hypothesis, we did not find an increased risk of many of the adverse perinatal outcomes we studied amongst at-risk pregnancies with abnormal fluid. There was an increased risk of NICU admission associated with polyhydramnios in normal and at-risk pregnancies.

Effect of Delayed Cord Clamping on Umbilical Blood Gas Values in Term Newborns: A Systematic Review

OBJECTIVE

To compare the effect of delayed cord clamping on cord blood gas values in vaginally delivered, healthy, term singletons.

DATA SOURCE

We used MEDLINE, CINAHL, CENTRAL, EMBASE, and ClinicalTrials.gov databases.

METHODS OF STUDY SELECTION

Eligible studies included randomized controlled trials (RCTs) comparing cord blood gas values obtained from early compared with delayed cord clamping groups and observational studies using serial cord blood gas from the same umbilical cord. We described the difference in means of cord blood gas parameters and comparative descriptive statistics when a difference in means was not available. We used a domain-based risk bias tool to extract methodologic details and assess potential risk of bias.

TABULATION, INTEGRATION, AND RESULTS

This review included two RCTs and three observational studies. These studies included a total of 234 newborns with early cord clamping and 218 newborns with delayed cord clamping. The observational studies showed that 45-90 seconds delayed cord clamping was associated with mean decreases in umbilical arterial pH (0.02-0.03), HCO3 (0.3-0.8 mmol/L) and increases in base deficit (0.3-1.3 mmol/L) compared with early cord clamping. One observational study showed that delayed cord clamping was associated with decreases in umbilical venous pH (0.01) and HCO3 (0.2 mmol/L) and increase in venous base deficit (0.1-0.3 mmol/L) compared with early cord clamping. These changes were not observed in the two RCTs.

CONCLUSION

Delayed cord clamping up to 120 seconds has either no effect or only a small effect on cord blood acid-base balance; overall, the magnitude of these changes is not clinically significant in vaginally delivered, healthy, term singletons.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO, CRD42019135779.

No. 197b-Fetal Health Surveillance: Intrapartum Consensus Guideline

OBJECTIVE

This guideline provides new recommendations pertaining to the application and documentation of fetal surveillance in the intrapartum period that will decrease the incidence of birth asphyxia while maintaining the lowest possible rate of obstetrical intervention. Pregnancies with and without risk factors for adverse perinatal outcomes are considered. This guideline presents an alternative classification system for antenatal fetal non-stress testing and intrapartum electronic fetal surveillance to what has been used previously. This guideline is intended for use by all health professionals who provide intrapartum care in Canada.

OPTIONS

Consideration has been given to all methods of fetal surveillance currently available in Canada.

OUTCOMES

Short- and long-term outcomes that may indicate the presence of birth asphyxia were considered. The associated rates of operative and other labour interventions were also considered.

EVIDENCE

A comprehensive review of randomized controlled trials published between January 1996 and March 2007 was undertaken, and MEDLINE and the Cochrane Database were used to search the literature for all new studies on fetal surveillance antepartum. The level of evidence has been determined using the criteria and classifications of the Canadian Task Force on Preventive Health Care (Table 1).

SPONSOR

This consensus guideline was jointly developed by the Society of Obstetricians and Gynaecologists of Canada and the British Columbia Perinatal Health Program (formerly the British Columbia Reproductive Care Program or BCRCP) and was partly supported by an unrestricted educational grant from the British Columbia Perinatal Health Program. RECOMMENDATION 1: LABOUR SUPPORT DURING ACTIVE LABOUR: RECOMMENDATION 2: PROFESSIONAL ONE-TO ONE CARE AND INTRAPARTUM FETAL SURVEILLANCE: RECOMMENDATION 3: INTERMITTENT AUSCULTATION IN LABOUR: RECOMMENDATION 4: ADMISSION FETAL HEART TEST: RECOMMENDATION 5: INTRAPARTUM FETAL SURVEILLANCE FOR WOMEN WITH RISK FACTORS FOR ADVERSE PERINATAL OUTCOME: When a normal tracing is identified, it may be appropriate to interrupt the electronic fetal monitoring tracing for up to 30 minutes to facilitate periods of ambulation, bathing, or position change, providing that (1) the maternal-fetal condition is stable and (2) if oxytocin is being administered, the infusion rate is not increased (III-B). RECOMMENDATION 6: DIGITAL FETAL SCALP STIMULATION: RECOMMENDATION 7: FETAL SCALP BLOOD SAMPLING: RECOMMENDATION 8: UMBILICAL CORD BLOOD GASES: RECOMMENDATION 9: FETAL PULSE OXIMETRY: RECOMMENDATION 10: ST WAVEFORM ANALYSIS: RECOMMENDATION 11: INTRAPARTUM FETAL SCALP LACTATE TESTING.

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.

Synchrotron X-ray fluorescence mapping of Ca, Sr and Zn at the neonatal line in human deciduous teeth reflects changing perinatal physiology

OBJECTIVES

Our first objective was to review the evidence describing the appearance and microstructure of the neonatal line in human deciduous teeth and to link this with known changes in neonatal physiology occurring at and around birth. A second objective was to explore ways to improve identification of the neonatal line by mapping the pre- and postnatal distribution of Ca, Sr and Zn in deciduous cuspal enamel and superimposing these maps onto transmitted light micrographs that included a clear true section of the neonatal line.

MATERIALS AND METHODS

We used synchrotron X-ray fluorescence to map elemental distributions in pre- and postnatal enamel and dentine. Two deciduous canines and 5 deciduous molars were scanned with an X-ray beam monochromatised to 17.0 keV at either 10.0, 2.5 or 1.0 μm resolution and 10 ms integration time.

RESULTS

Calcium maps distinguished enamel and dentine but did not clearly demarcate tissues formed pre- or postnatally. Strontium maps reflected presumed pre- and postnatal maternal serum levels and what are likely to be diet-dependent regions of Sr enrichment or depletion. Prenatal Zn maps, particularly for dentine, mirror elevated levels in the fetus and in colostrum during the first few days of life.

CONCLUSIONS

The neonatal line, enamel dentine junction and surface enamel were all Zn-rich. Within the neonatal line Zn may be associated with increased crystallinity but also with caries resistance, both of which have been reported previously. Elemental mapping may improve the identification of ambiguous NNLs and so be useful in forensic and archaeological studies.

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.

Neonatal Morbidities of Fetal Growth Restriction: Pathophysiology and Impact

Being born small lays the foundation for short-term and long-term implications for life. Intrauterine or fetal growth restriction describes the pregnancy complication of pathological reduced fetal growth, leading to significant perinatal mortality and morbidity, and subsequent long-term deficits. Placental insufficiency is the principal cause of FGR, which in turn underlies a chronic undersupply of oxygen and nutrients to the fetus. The neonatal morbidities associated with FGR depend on the timing of onset of placental dysfunction and growth restriction, its severity, and the gestation at birth of the infant. In this review, we explore the pathophysiological mechanisms involved in the development of major neonatal morbidities in FGR, and their impact on the health of the infant. Fetal cardiovascular adaptation and altered organ development during gestation are principal contributors to postnatal consequences of FGR. Clinical presentation, diagnostic tools and management strategies of neonatal morbidities are presented. We also present information on the current status of targeted therapies. A better understanding of neonatal morbidities associated with FGR will enable early neonatal detection, monitoring and management of potential adverse outcomes in the newborn period and beyond.

Incidence of newborn resuscitative interventions at birth and short-term outcomes: a regional population-based study

OBJECTIVES

To determine the incidence and characteristics of resuscitative interventions at different gestational ages and short-term outcomes after resuscitation.

DESIGN SETTING AND PATIENTS

A prospective observational study in an unselected population at Stavanger University Hospital, Norway, from October 2016 until September 2017.

INTERVENTIONS

Using a data collection form and video recordings, we registered and analysed resuscitative interventions.

MAIN OUTCOME MEASURES

Incidence of continuous positive airway pressure (CPAP), positive pressure ventilation (PPV), intubation, chest compressions and intravenous fluid or epinephrine boluses. Short-term outcomes of resuscitated newborns.

RESULTS

All 4693 newborns in the study period were included in the study. Two hundred and ninety-one (6.2%) newborns received interventions in the first minutes of life beyond drying and stimulation. PPV was provided in 170 (3.6%) while CPAP (without PPV) was provided in 121 (2.6%) newborns. Duration of PPV was median (IQR) 106 s (54-221). Intubations were performed in 19 (0.4%) newborns, with a mean (SD) intubation time of 47 (21) s. Ten (0.2%) newborns received chest compressions and epinephrine was administrated in three (0.1%) newborns. Sixty-three per cent of the treated newborns from 34 weeks' gestational age were returned to parental care without further follow-up.

CONCLUSIONS

The need for resuscitative interventions after birth was frequent in this unselected population in a high-resource setting, but full cardiopulmonary resuscitation was rare. Short-term outcomes were good, suggesting that most newborns treated with resuscitative interventions were not severely affected.

Re-examining the arterial cord blood gas pH screening criteria in neonatal encephalopathy

OBJECTIVE

Screening criteria for neonatal encephalopathy remain a complex combination of subjective and objective criteria. We examine the utility of universal cord blood gas testing and mandatory encephalopathy evaluation for infants with pH ≤7.10 on umbilical cord arterial blood gas (cABG) as a single screening measure for timely identification of moderate/severe encephalopathy.

DESIGN, SETTING, PATIENTS

Infants born at a single centre between 2008 and 2015, who were ≥36 weeks, had no congenital anomalies and had a cABG pH ≤7.10 were identified for a retrospective cohort study. Maternal/perinatal and patient factors were collected.

RESULTS

27 028 infants were born during the study period; 412 met all inclusion criteria. Of those, 35/85 infants with pH <7.00 and 34/327 infants with pH between 7.00 and 7.10 had moderate/severe encephalopathy. Encephalopathy was identified on the basis of pH and examination alone (no other perinatal criteria present) in 5/35 and 13/34 infants in the two pH groups, respectively.A cABG pH threshold of ≤7.10 was associated with a sensitivity of 74.2% and a specificity of 98.7% for detection of moderate/severe encephalopathy. Based on these data, 25 infants with cABG pH between 7.00 and 7.10 will need to be screened to identify one neonate with moderate/severe encephalopathy, who might have otherwise been missed using conventional screening, a 15% increase in appropriate selection and treatment over current methods.

CONCLUSION

Universal cord blood gas screening with a pH threshold ≤7.10 and mandatory encephalopathy examination results in greater detection of infants with moderate/severe encephalopathy and timely initiation of therapeutic hypothermia.

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.

Birth parameters and parental height predict growth outcome in children with chronic kidney disease

BACKGROUND

We analyzed the impact of birth parameters and parental height on long-term growth outcome in children with chronic kidney disease (CKD) stage 3-5.

METHODS

Linear growth was prospectively investigated in 509 children, with a mean follow-up of 4.1 years. Growth outcome was categorized in (i) poor growth (PG): height standard deviation score (SDS) during follow-up < -2.0 and/or actual or previous growth hormone (GH) treatment, and (ii) good growth (GG): height SDS ≥ -2.0 and no need for GH. A multivariate binary logistic regression model was constructed for predictors of PG outcome.

RESULTS

PG was observed in 55 % of patients. The rate of pre-term and small for gestational age birth was significantly higher in children with PG compared to GG (43.2 vs. 25.6 % and 36.8 vs. 18.9 %; p < 0.001). Children with PG had significantly lower average values for gestational age, birth weight, length, and head circumference, umbilical cord pH, Apgar scores, and parental height than children with GG. Birth length, umbilical cord pH, and parental height were significant independent predictors of PG outcome (sensitivity 72.8 %, specificity 69.3 %).

CONCLUSIONS

Birth parameters and parental height are independent predictors of growth outcome in children with CKD.

Clinical associations with uterine tachysystole

OBJECTIVES

To determine the incidence of uterine tachysystole (UT) and its association with neonatal depression or metabolic acidemia (DEP).

METHODS

This retrospective study comprised all 6234 women at ≥ 37 weeks' gestation who were monitored during the last 4 hours of tracings before birth in an academic community hospital. DEP was defined by an umbilical artery base deficit value ≥ 10 mmol/L or a 5-minute Apgar ≤ 6 and included 77 births. UT was defined by >15 contractions in 30 minutes.

RESULTS

The overall incidence of UT was 18.3% (1139/6234). In 4.2% (260/6234) UT persisted for >60 min. The rate of UT was similar in births with DEP (14.3%, 11/77) compared to those without DEP (18.3%, 1128/6157; p=0.45). In births with UT, only 1.0% (11/1139) developed DEP. The DEP group had more decelerations at almost every level of contractions and a higher cesarean rate of 49.4% (38/77) compared to 24.0% (1468/6124); p=<0.001 in the group without DEP.

CONCLUSIONS

UT was common, occasionally prolonged and almost always benign. Fetuses with DEP had no more UT than those without DEP. Many babies with DEP declared their vulnerability with decelerations at contraction rates below UT levels and the great majority of them never experienced UT.

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.

Anesthesia for fetal surgery

Fetal surgery pushes the limits of knowledge and therapy beyond conventional paradigms by treating the developing fetus as a patient. Providing anesthesia for fetal surgery is challenging for many reasons. It requires integration of both obstetric and pediatric anesthesia practice. Two patients must be anesthetized for the benefit of one, and there is little margin for error. Many disciplines are involved, and communication must be effective among all of them. Conducting anesthetic research with vulnerable populations, such as the pregnant woman carrying a fetus with a birth defect is difficult, and many questions remain to be answered. Work is needed to study possible neurotoxicity caused by exposure of the developing brain to anesthetic agents. The effects of stress on the developing fetus also must be further delineated. Anesthetic techniques vary by institution, and prospective studies to determine optimal anesthetic regimens are warranted.

Relationship between oxygen saturation and umbilical cord pH immediately after birth

BACKGROUND

The aim of this study is to determine the relationship between oxygen saturation (SpO(2)) by pulse oximetry levels and umbilical cord arterial pH values in healthy newborns during the first 15 minutes of life.

METHODS

The study was performed with healthy term, appropriate-for-gestational-age newborn infants. The infants were divided in two groups: umbilical cord arterial blood pH value ≤7.19 (group 1) and >7.19 (group 2); SpO(2) levels during the first 15 minutes of life were compared between groups.

RESULTS

The study was completed with 129 infants (33 in group 1 and 96 in group 2). A significant correlation was found between first-measured preductal and postductal SpO(2) levels by pulse oximetry and umbilical cord arterial pH values ([r²:0.72(0.62 -0.79); p < 0.001] and [r²:0.32(0.25 - 0.54); p < 0.001], respectively). In group 1, infants had lower SpO(2) levels at both preductal and postductal measurements during the first 11 minutes of life and time to reach ≥90% SpO(2) level was longer compared with infants in group 2.

CONCLUSION

Determination of umbilical arterial blood pH values, in addition to clinical findings and oxygen saturation measurements, might be helpful in deciding the concentration of oxygen and whether or not to continue oxygen supplementation in the delivery room.

End tidal carbon dioxide levels during the resuscitation of prematurely born infants

BACKGROUND

Successful resuscitation of prematurely born infants is dependent on achieving adequate alveolar ventilation and vasodilation of the pulmonary vascular bed. Elevation of end-tidal carbon dioxide (ETCO(2)) levels may indicate pulmonary vasodilation.

AIMS

This research aims to study the temporal changes in ETCO(2) levels and the infant's respiratory efforts during face mask resuscitation in the labour suite, and to determine if the infant's first inspiratory effort was associated with a rise in the ETCO(2) levels, suggesting pulmonary vasodilation had occurred.

STUDY DESIGN

This study is an observational one.

SUBJECTS

The subjects of the study are forty infants with a median gestational age of 30 weeks (range 23-34).

OUTCOME MEASURES

Inflation pressures, expiratory tidal volumes and ETCO(2) levels were measured.

RESULTS

The median expiratory tidal volume of inflations prior to the onset of the infant's respiratory efforts (passive inflations) was lower than that of the inflation associated with the first inspiratory effort (active inflation) (1.8 (range 0.1-7.3) versus 6.3 ml/kg (range 1.9-18.4), p<0.001), as were the median ETCO(2) levels (0.3 (range 0.1-2.1) versus 3.4 kPa (0.4-11.5), p<0.001). The median expiratory tidal volume (4.5 ml/kg (range 0.5-18.3)) and ETCO(2) level (2.2 kPa (range 0.3-9.3)) of the two passive inflations following the first active inflation were also higher than the median expiratory tidal volume and ETCO(2) levels of the previous passive inflations (p<0.001, p<0.0001 respectively).

CONCLUSION

These results suggest that during face mask resuscitation, improved carbon dioxide elimination, likely due to pulmonary vasodilation, occurred with the onset of the infant's respiratory efforts.

High uterine contraction rates in births with normal and abnormal umbilical artery gases

OBJECTIVE

To determine if the incidence of high contraction (HC) rates and associated decelerations were different in term births with metabolic acidemia (MA) compared to those with normal gases (N) over the last 4 h of labor.

METHODS

MA included 316 babies with cord base deficits (BD) over 12 mmol/L N - 3,320 babies with BD under 8 mmol/L. HC rates were defined as >5/10 min.

RESULTS

One or more episodes of HC occurred in 43.7% of MA and 36.6% of N. (p = 0.015) In both groups the HC rates rose from about 1 in 30 patients at the beginning to 1 in 7 to 9 patients at the end. MA showed a different transition of the deceleration response over time. At the beginning the average ratio of decelerations to uterine contractions was similar in both groups but over the final 140 min MA showed a consistently higher ratio.

CONCLUSIONS

Although HC rates were more frequent in the MA, it was not uncommon in N. On average MA showed more decelerations at every level of contractions and had a persistently higher level of decelerations per contraction for more than 2 h before birth.

Update in fetal anesthesia for the ex utero intrapartum treatment (EXIT) procedure

The ex-utero intrapartum treatment (EXIT) is one type of fetal surgery, performed before delivery while the fetus remains attached to the uteroplacental circulation. This intervention improves neonatal morbidity and mortality of certain congenital diseases. For instance, securing the airway of a fetus with congenital airway obstruction while on uteroplacental circulation prevents the hypoxemia during the establishment of an airway post-delivery. Anesthesia for fetal surgery now incorporates new knowledge of the maternal/fetal response to anesthetic agents. This chapter reviews for the EXIT procedure the effects of maternal anesthesia on fetal hemodynamics, intravenous anesthesia to supplement inhalational anesthesia in order to provide maternal-fetal hemodynamic stability during surgery, intraoperative fetal monitoring, maternal pharmacokinetics approach to study placental drug transfer and fetal pharmacokinetics to improve our understanding of the effects of maternal anesthesia on the fetus.

Persistent organochlorine compounds in fetal and maternal tissues: evaluation of their potential influence on several indicators of fetal growth and health

Some organochlorine compounds, such as polychlorinated biphenyls (PCBs), have a tendency to bioaccumulate in humans and predators at the top of the food chain. We have recently confirmed the transplacental transfer of these compounds and the present study has been designed on the same material with the aim of investigating their potential health effects on newborns from 70 pregnant women, resident in a Northern Italy industrial town. Organochlorine compounds [namely, p,p'-dichlorodiphenyltrichloroethane (p,p'-DDT), p,p'-dichlorodiphenyldichloroethene (p,p'-DDE), hexachlorobenzene (HCB), and PCBs] have been analyzed both in cord and maternal serum, placenta, and maternal subcutaneous adipose tissue by GC-MSD. p,p'-DDT levels in the adipose tissue resulted significantly (p<0.05) related to birth length. Mothers of neonates born by preterm programmed caesarean delivery showed significantly (p<0.005 for both) higher serum p,p'-DDE serum concentrations and p,p'-DDT levels in the adipose tissue, as compared to mothers delivering at term.

Re-evaluation of cord blood arterial and venous reference ranges for pH, pO(2), pCO(2), according to spontaneous or cesarean delivery

Umbilical cord blood gas analysis (pO(2) and pCO(2)) is now recommended in all high-risk baby deliveries and in some centers it is performed routinely following all deliveries. The aim of this study was to re-evaluate cord blood arterial and venous reference ranges for pH, pO(2), pCO(2) in newborns, delivered by spontaneous vaginal delivery (SVD) and by cesarean section (CS) performed in Faculty Hospital Motol. Two groups of subjects were selected for the study. Group I consisted of 303 newborns with SVD. Group II consisted of 189 newborns delivered by cesarean section. Cord blood samples were analyzed for standard blood gas and pH, using the analytical device Rapid Lab 845 and Rapid Lab 865. We obtained reference values expressed as range (lower and upper reference value expressed as 2.5 and 97.5 percentiles) for cord blood in newborns with SVD: arterial cord blood: pH=7.01-7.39; pCO(2)=4.12-11.45 kPa; pO(2)=1.49-5.06 kPa; venous cord blood: pH=7.06-7.44; pCO(2)=3.33-9.85 kPa; pO(2)=1.80-6.29 kPa. We also obtained reference values for cord blood in newborns delivered by CS: arterial cord blood: pH=7.05-7.39; pCO(2)=5.01-10.60 kPa; pO(2)=1.17-5.94 kPa; venous cord blood: pH=7.10-7.42; pCO(2)=3.88-9.36 kPa; pO(2)=1.98-7.23 kPa. Re-evaluated reference ranges play essential role in monitoring conditions of newborns with spontaneous and caesarean delivery.

Pre- and perinatal predictors of startle eye blink reaction and prepulse inhibition in healthy neonates

The present study examined the startle eye blink reflex and prepulse inhibition (PPI) in 65 healthy term-born neonates. Although the startle eye blink is already present at birth, some relevant neuronal structures are not fully mature. We therefore investigated the relationship between prenatal maturation and perinatal stress experience on startle eye blink and PPI. Eye blinks were evoked by unilaterally presented acoustic broadband white noise (50 ms, 95 dB, prepulse 75 dB). Startle response magnitude and percent PPI were calculated for ipsilateral and contralateral side of stimulation. Neonates exhibited stronger startle responses ipsilaterally than contralaterally, and a significant PPI. Neonates with more prenatal growth and less perinatal stress had greater startle magnitudes. Neonates with more stress had more PPI contralaterally. Results suggest that startle eye blinks may be useful as indicators of prenatal maturation and perinatal stress.

Neonatal outcomes and operative vaginal delivery versus cesarean delivery

We compared outcomes for neonates with forceps-assisted, vacuum-assisted, or cesarean delivery in the second stage of labor. This is a secondary analysis of a randomized trial in laboring, low-risk, nulliparous women at >or=36 weeks' gestation. Neonatal outcomes after use of forceps, vacuum, and cesarean were compared among women in the second stage of labor at station +1 or below (thirds scale) for failure of descent or nonreassuring fetal status. Nine hundred ninety women were included in this analysis: 549 (55%) with an indication for delivery of failure of descent and 441 (45%) for a nonreassuring fetal status. Umbilical cord gases were available for 87% of neonates. We found no differences in the base excess (P = 0.35 and 0.78 for failure of descent and nonreassuring fetal status) or frequencies of pH below 7.0 (P = 0.73 and 0.34 for failure of descent and nonreassuring fetal status) among the three delivery methods. Birth outcomes and umbilical cord blood gas values were similar for those neonates with a forceps-assisted, vacuum-assisted, or cesarean delivery in the second stage of labor. The occurrence of significant fetal acidemia was not different among the three delivery methods regardless of the indication.

Graded classification of fetal heart rate tracings: association with neonatal metabolic acidosis and neurologic morbidity

OBJECTIVE

The objective of the study was to measure the performance of a 5-tier, color-coded graded classification of electronic fetal monitoring (EFM).

STUDY DESIGN

We used specialized software to analyze and categorize 7416 hours of EFM from term pregnancies. We measured how often and for how long each of the color-coded levels appeared in 3 groups of babies: (A) 60 babies with neonatal encephalopathy (NE) and umbilical artery base deficit (BD) levels were greater than 12 mmol/L; (I) 280 babies without NE but with BD greater than 12 mmol/L; and (N) 2132 babies with normal gases.

RESULTS

The frequency and duration of EFM abnormalities considered more severe in the classification method were highest in group A and lowest in group N. Detecting an equivalent percentage of cases with adverse outcomes required only minutes spent with marked EFM abnormalities compared with much longer periods with lesser abnormalities.

CONCLUSION

Both degree and duration of tracing abnormality are related to outcome. We present empirical data quantifying that relationship in a systematic fashion.

Anesthesia for fetal surgery

Fetal surgery pushes the limits of knowledge and therapy beyond conventional paradigms by treating the developing fetus as a patient. Providing anesthesia for fetal surgery is challenging for many reasons. It requires integration of both obstetric and pediatric anesthesia practice. Two patients must be anesthetized for the benefit of one, and there is little margin for error. Many disciplines are involved, and communication must be effective. Conducting anesthetic research with vulnerable populations, such as pregnant women and their fetuses, is difficult, and many questions remain unanswered. Work must be done in the study of possible neurotoxicity caused by exposure of developing brain to anesthetic agents. The effects of stress on the developing fetus must also be further examined. Optimal anesthetic regimens remain to be determined.

Reference values for strong ion difference--a novel tool for fetal metabolic assessment

OBJECTIVES

The aim of this pilot study was to establish reference values for strong ion difference (SID) in umbilical cord blood and investigate the feasibility of evaluating fetal metabolism according to the comprehensive approach to acid-base abnormalities, based on Stewart's physiochemical theory.

STUDY DESIGN

A prospective observational study. Women who underwent an elective cesarean section at term (n=40) were compared to women who completed a normal spontaneous delivery at term (n=40). The primary outcome was the establishment of normal values for SID in the umbilical cord vein. We also compared acid-base variables in the umbilical vein between the groups.

RESULTS

The apparent SID in the umbilical vein was 34.61+/-3.92 mequiv./L after normal delivery and 35.98+/-2.56 mequiv./L after elective cesarean section (the effective SID is 37.43+/-1.93 and 38.29+/-2.38 mequiv./L, respectively). The pH values were similar in both groups, but the pCO(2) was significantly higher and the plasma principal weak acids (albumin and phosphate) were significantly lower after cesarean sections.

CONCLUSIONS

SID enables a comprehensive approach to acid-base abnormalities in the neonate, making it a potential additional tool for evaluating fetal acid-base status.

Neonatal lines in the enamel of primary teeth--a morphological and scanning electron microscopic investigation

OBJECTIVE

The neonatal line (NNL) is in principle found in all primary teeth and the line represents the time of birth. Earlier findings of the appearance of the NNL in light microscope and in microradiographs have shown not only changes in the prism direction of the enamel, but that the NNL has a hypomineralized character.

METHODS

The neonatal line was analyzed in un-decalcified sections of primary lower and central incisors, collected from individuals of different ages utilizing polarized light microscopy, microradiography, scanning electron microscopy (SEM) and X-ray analysis (XRMA).

RESULTS

In polarized light the NNL appeared to have a more porous structure than the enamel in general. The appearance of the NNL as a dark line in microradiographs is interpreted as the NNL being less mineralized than neighbouring enamel. Analysis with ImageJ visualized the reduction of the amount of grey value, indicating that the NNL is less mineralized. Analysis of the NNL in SEM showed a reduction of the diameter of enamel prisms, the more narrow diameters continued through the postnatal enamel. A change of the growth direction of the prisms was also observed at the NNL. In a three-dimensional image the NNL appeared as a grove, however, in non-etched enamel no grove was seen. The elemental analyses with XRMA showed no marked changes in the content of C, Ca, P, N, O or S in the area around the NNL.

CONCLUSIONS

The NNL is an optical phenomenon due to alterations in height, and degree of mineralization of the enamel prisms.