Intrapartum fetal pulse oximetry: fetal oxygen saturation trends during labor and relation to delivery outcome

Thrombotic Alterations under Perinatal Hypoxic Conditions: HIF and Other Hypoxic Markers

Hypoxia is considered to be a stressful physiological condition, which may occur during labor and the later stages of pregnancy as a result of, among other reasons, an aged placenta. Therefore, when gestation or labor is prolonged, low oxygen supply to the tissues may last for minutes, and newborns may present breathing problems and may require resuscitation maneuvers. As a result, poor oxygen supply to tissues and to circulating cells may last for longer periods of time, leading to life-threatening conditions. In contrast to the well-known platelet activation that occurs after reperfusion of the tissues due to an ischemia/reperfusion episode, platelet alterations in response to reduced oxygen exposition following labor have been less frequently investigated. Newborns overcome temporal hypoxic conditions by changing their organ functions or by adaptation of the intracellular molecular pathways. In the present review, we aim to analyze the main platelet modifications that appear at the protein level during hypoxia in order to highlight new platelet markers linked to complications arising from temporal hypoxic conditions during labor. Thus, we demonstrate that hypoxia modifies the expression and activity of hypoxic-response proteins (HRPs), including hypoxia-induced factor (HIF-1), endoplasmic reticulum oxidase 1 (Ero1), and carbonic anhydrase (CIX). Finally, we provide updates on research related to the regulation of platelet function due to HRP activation, as well as the role of HRPs in intracellular Ca2+ homeostasis.

The impact of maternal diabetes on birth to placental weight ratio and umbilical cord oxygen values with implications for fetal-placental development

INTRODUCTION

We determined the impact of gestational diabetes (GDM) and pre-existing diabetes (DM) on birth/placental weight and cord oxygen values with implications for placental efficiency and fetal-placental growth and development.

METHODS

A hospital database was used to obtain birth/placental weight, cord PO₂ and other information on patients delivering between Jan 1, 1990 and Jun 15, 2011 with GA >34 weeks (N = 69,854). Oxygen saturation was calculated from the cord PO₂ and pH data, while fetal O₂ extraction was calculated from the oxygen saturation data. The effect of diabetic status on birth/placental weight and cord oxygen values was examined adjusting for covariates.

RESULTS

Birth/placental weights were stepwise decreased in GDM and DM compared to non-diabetics with placentas disproportionally larger indicating decreasing placental efficiency. Umbilical vein oxygen was marginally increased in GDM but decreased in DM attributed to the previously reported hyper-vascularization in diabetic placentas with absorbing surface area of capillaries initially increased, but then constrained by increasing distance from maternal blood within the intervillous space. Umbilical artery oxygen was unchanged in GDM and DM, with fetal O₂ extraction decreased in DM indicating that fetal O₂ delivery must be increased relative to O₂ consumption and likely due to increased umbilical blood flow.

DISCUSSION

Increased villous density/hyper-vascularization in GDM and DM with placentas disproportionately larger and umbilical blood flow increased, are postulated to normalize umbilical artery oxygen despite increased birth weights and growth-related O₂ consumption. These findings have implications for mechanisms signaling fetal-placental growth and development in diabetic pregnancies and differ from that reported with maternal obesity.

Fetal sex impacts birth to placental weight ratio and umbilical cord oxygen values with implications for regulatory mechanisms

Background

We determined the effect of fetal sex on birth/placental weight and umbilical vein and artery oxygen values with implications for placental efficiency and regulatory mechanisms underlying fetal–placental growth differences.

Methods

A hospital database was used to obtain birth/placental weight, cord PO₂ and other information on patients delivering between Jan 1, 1990 and Jun 15, 2011 with GA > 34 weeks (N = 69,836). Oxygen saturation was calculated from the cord PO₂ and pH data, while fractional O₂ extraction was calculated from the oxygen saturation data. The effect of fetal sex on birth/placental weight, cord PO₂, O₂ saturation, and fractional O₂ extraction was examined in all patients adjusting for pregnancy and labor/delivery covariates, and in a subset of low-risk patients.

Results

Birth/placental weights were lower in females indicating decreased placental efficiency. Umbilical vein oxygen values were higher in females attributed to increased uterine blood flow, while artery oxygen values were lower in females attributed to decreased hemoglobin and umbilical blood flow, and increased oxygen consumption. Fetal O₂ extraction was increased in females confirming increased O₂ consumption relative to delivery.

Conclusions

Sex-related differences in uterine/umbilical blood flows, placental development, and fetal O₂ consumption can be linked to the differences observed in cord oxygen. The lower umbilical artery oxygen in females as a measure of systemic oxygenation signaling growth could account for their decreased birth weights, while slower development in female placentae could account for their lower placental weights, which could be differentially effected contributing to their lower birth/placental weights.

Birth/placental wt is decreased in females as a measure of placental efficiency.

Cord vein O₂ is increased in females as a measure of placental O₂ transport.

Cord artery O₂ is decreased in females as a measure of fetal systemic O₂ levels.

Sex differences in placental development link to cord O₂-birth/placental wt findings.

Gestational age impacts birth to placental weight ratio and umbilical cord oxygen values with implications for the fetal oxygen margin of safety

BACKGROUND

We determined the impact of gestational age (GA) from near term to term to post-term on birth/placental weight ratio and cord oxygen values with implications for placental transport efficiency for oxygen, fetal O₂ consumption relative to delivery or fractional O₂ extraction, and oxygen margin of safety.

MATERIALS AND METHODS

A hospital database was used to obtain birth/placental weight ratios, cord PO₂ and other information on patients delivering between Jan 1, 1990 and Jun 15, 2011 with GA > 34 completed weeks (N = 69,852). Oxygen saturation was calculated from the cord PO₂ and pH data, while fractional O₂ extraction was calculated from the oxygen saturation data. The effect of GA grouping on birth/placental weight ratio, cord PO₂, O₂ saturation, and fractional O₂ extraction values, was examined in all patients adjusting for pregnancy and labor/delivery covariates, and in a subset of low-risk patients.

RESULTS

Birth/placental weight ratio and umbilical venous O₂ values increased with advancing GA, supporting the conjecture of increasing placental transport efficiency for oxygen. However, umbilical arterial O₂ values decreased while fractional O₂ extraction increased with successive GA groupings, indicating that fetal O₂ consumption must be increasing relative to delivery.

CONCLUSIONS

Fetal O₂ consumption can be seen as ever 'outgrowing' O₂ delivery over the last weeks of pregnancy and leading to a continued lowering in systemic oxygen levels. While this lowering in oxygen may trigger feedback mechanisms with survival benefit, the 'oxygen margin of safety' will also be lowered increasing perinatal morbidity and mortality which appear to be hypoxia related.

Predicting Outcome in Neonates with Possible Clinical Sepsis by Estimating an Early Score for Neonatal Acute Physiology-II (SNAP-II)

OBJECTIVES

To determine role of Score for Neonatal Acute Physiology-II (SNAP-II) and its individual parameters assessed within 12 h of suspicion of neonatal sepsis in predicting outcomes; study its distribution across gestational ages and determine its relation with survival duration among expired neonates.

METHODS

This prospective observational study conducted in a newborn unit of a tertiary care teaching hospital over 1 year included intramural neonates with birth weight ≥1000 g and gestation ≥28 weeks suspected with sepsis and assigned SNAP-II score within 12 h of suspicion. On day 14 of enrollment, they were categorized into three outcome groups: death (D), survival with organ dysfunction (SOD) and survival without organ dysfunction (SWOD).

RESULTS

One hundred and ten neonates were enrolled and 100 analyzed. Mean SNAP-II score was 22 ± 22 (median: 13; interquartile range: 5-32.5). Seventy-six percent, 16% and 8% neonates belonged to SWOD, D and SOD groups, respectively. SNAP-II score and its individual parameters varied significantly among all outcome groups (p < 0.001). SNAP-II cutoffs of 44/115, 44/115, 38/115 and 33/115 were found to be highly predictive of D, D vs. SOD, D/SOD vs. SWOD and SWOD vs. SOD, respectively (sensitivity: 87.5-99%; specificity: 75-99%). The score was unaffected by gestational age (p = 0.80). Neonates with culture positive sepsis/meningitis had higher SNAP-II scores (p = 0.001).

CONCLUSIONS

SNAP-II and its individual parameters found to have high sensitivity and specificity in predicting outcomes in possible neonatal sepsis and may have a role in predicting severity of disease progression and rapidity of deterioration among non-survivors, pending validation in larger studies.

Optimizing oxygen therapy for preterm infants at birth: Are we there yet?

Premature infants undergo a complex postnatal adaptation at birth. For last two centuries, oxygen has been integral to respiratory support of preterm infants at birth. Excess oxygen can cause oxidative stress and tissue injury. Preterm infants due to lung immaturity may need oxygen for successful transition at birth. Although, considerable progress has been made in the last 3 decades, optimum oxygen therapy for preterm delivery room resuscitation remains unknown. In this review, we discuss the history and physiology behind oxygen therapy in the delivery room, evaluate current literature, provide practice points and point out knowledge gaps of oxygen therapy in preterm infant at birth.

Haemodynamic Instability and Brain Injury in Neonates Exposed to Hypoxia⁻Ischaemia

Brain injury in the asphyxic newborn infant may be exacerbated by delayed restoration of cardiac output and oxygen delivery. With increasing severity of asphyxia, cerebral autoregulatory responses are compromised. Further brain injury may occur in association with high arterial pressures and cerebral blood flows following the restoration of cardiac output. Initial resuscitation aims to rapidly restore cardiac output and oxygenation whilst mitigating the impact of impaired cerebral autoregulation. Recent animal studies have indicated that the current standard practice of immediate umbilical cord clamping prior to resuscitation may exacerbate injury. Resuscitation prior to umbilical cord clamping confers several haemodynamic advantages. In particular, it retains the low-resistance placental circuit that mitigates the rebound hypertension and cerebrovascular injury. Prolonged cerebral hypoxia–ischaemia is likely to contribute to further perinatal brain injury, while, at the same time, tissue hyperoxia is associated with oxidative stress. Efforts to monitor and target cerebral flow and oxygen kinetics, for example, using near-infrared spectroscopy, are currently being evaluated and may facilitate development of novel resuscitation approaches.

Reevaluation of intrapartum fetal monitoring using fetal oximetry: A review

AIM

Although several studies reported the measurement of fetal oxygen saturation using fetal pulse oximetry (FPO) for evaluation of the fetal intrapartum condition, a systematic review of the seven randomized controlled trials (RCTs) provided no evidence to support FPO for intrapartum fetal monitoring. In the present review, we re-evaluate an overview for the use of FPO and seven RCTs of FPO.

METHODS

We reviewed numerous previous reports on FPO and seven RCTs of intrapartum FPO. RCTs were conducted with the main outcome measure being a reduction in the cesarean section rate.

RESULTS

The largest trial with 5341 entries failed to show any reduction. The negative result from this RCT may be explained by the use of a different cutoff value for fetal oxygen saturation compared to the other RCT; in addition, there were differences in the indications for cesarean section due to dystocia and in the definition of non-reassuring fetal status (NRFS). An abnormal FPO value, defined as the fetal oxygen saturation value <30% for at least 10 min, is useful for making a diagnosis of fetal acidosis. A newly developed device, an examiner's finger-mounted tissue oximetry, accurately measures tissue oxygen saturation while overcoming the drawbacks of FPO, such as infection risk and slipping off of the sensor during descent of the fetal head.

CONCLUSION

FPO (including the new device) with fetal heart rate monitoring in selected cases of NRFS may reduce the cesarean section rate.

Oxygen Therapy in the Delivery Room: What Is the Right Dose?

Oxygen is the most commonly used medicine used during neonatal resuscitation in the delivery room. Oxygen therapy in delivery room should be used judiciously to avoid oxygen toxicity while delivering sufficient oxygen to prevent hypoxia. Measurement of appropriate oxygenation relies on pulse oximetry, but adequate ventilation and perfusion are equally important for oxygen delivery. In this article, we review oxygenation while transitioning from fetal to neonatal life, the importance of appropriate oxygen therapy, its measurement in the delivery room, and current recommendations for oxygen therapy and its limitations.

Intrauterine resuscitation during the second stage of term labour by maternal hyperoxygenation versus conventional care: study protocol for a randomised controlled trial (INTEREST O2)

BACKGROUND

Perinatal asphyxia is, even in developed countries, one the major causes of neonatal morbidity and mortality. Therefore, if foetal distress during labour is suspected, one should try to restore foetal oxygen levels or aim for immediate delivery. However, studies on the effect of intrauterine resuscitation during labour are scarce. We designed a randomised controlled trial to investigate the effect of maternal hyperoxygenation on the foetal condition. In this study, maternal hyperoxygenation is induced for the treatment of foetal distress during the second stage of term labour.

METHODS/DESIGN

This study is a single-centre randomised controlled trial being performed in a tertiary hospital in The Netherlands. From among cases of a suboptimal or abnormal foetal heart rate pattern during the second stage of term labour, a total of 116 patients will be randomised to the control group, where normal care is provided, or to the intervention group, where before normal care 100% oxygen is supplied to the mother by a non-rebreathing mask until delivery. The primary outcome is change in foetal heart rate pattern. Secondary outcomes are Apgar score, mode of delivery, admission to the neonatal intensive care unit and maternal side effects. In addition, blood gas values and malondialdehyde are determined in umbilical cord blood.

DISCUSSION

This study will be the first randomised controlled trial to investigate the effect of maternal hyperoxygenation for foetal distress during labour. This intervention should be recommended only as a treatment for intrapartum foetal distress, when improvement of the foetal condition is likely and outweighs maternal and neonatal side effects.

TRIAL REGISTRATION

EudraCT, 2015-001654-15; registered on 3 April 2015. Dutch Trial Register, NTR5461; registered on 20 October 2015.

Maternal body mass index impacts fetal-placental size at birth and umbilical cord oxygen values with implications for regulatory mechanisms

BACKGROUND

Maternal under- and over-nutrition are known to effect fetal growth with altered placental development and nutrient transport, but whether fetal oxygenation is also altered remains unknown.

AIMS

To examine linkages between maternal BMI and birth weights, placental weights, and umbilical vein and artery PO_2, with implications for signaling mechanisms.

STUDY DESIGN

Population-based cohort study.

SUBJECTS

Analysis of hospital database information on all patients with pre-pregnant BMI values delivering viable, singleton infants between Jan 1, 1999 and Dec 31, 2010 (N=29,212). BMI was categorized into underweight, normal weight, overweight, and obese, with birth weights categorized into small (SGA), appropriate (AGA), and large for gestational age (LGA).

OUTCOME MEASURES

Maternal BMI, birth and placental weights, umbilical vein and artery PO₂.

RESULTS

Underweight mothers with smaller infants and overweight/obese mothers with larger infants had disproportionately large placentas, suggesting compensatory and/or enhanced placental growth in these pregnancies. All SGA infants had lower umbilical vein and artery PO₂, consistent with aberrant placental development leading to diffusional impairment of oxygen. Both maternal overweight/obese BMI and LGA resulted in lower artery PO₂, likely due to increased growth rates with the larger size in these infants.

CONCLUSIONS

These findings support fetal hypoxemia as a common determinant of growth restriction, whether in underweight mothers and due to under-nutrition or in overweight/obese mothers and due to placental insufficiency. However, oxygen is unlikely to be the primary promotor for fetal growth in overweight/obese mothers and LGA infants, with other substrates of more importance as nutritional cues in these pregnancies.

Examiner's finger-mounted fetal tissue oximetry: a preliminary report on 30 cases

OBJECTIVE

To describe preliminary experience with a finger-mounted fetal tissue oximetry probe during the 2nd stage of labor.

MATERIALS AND METHODS

A total of 30 term pregnant women without pregnancy complications were recruited. We measured fetal tissue oxygen saturation (FtO2) by using a finger-mounted fetal tissue oximetry during cervical examinations in the 2nd stage of labor. The data capturing rate of FtO2 and the interclass correlation coefficient were also examined. The mean FtO2 was compared to the neonatal condition assessed by the levels of umbilical cord blood.

RESULTS

FtO2 was obtained in all cases, regardless of wetness, hair color, the part of the fetal head that was exposed, rotation of the fetus, color of amniotic fluid, and caput succedaneum. The mean FtO2 was 65.5%±8.58% in normal neonates [Apgar score >7 (1 min), n=25]. The mean FtO2 was significantly correlated with umbilical cord arterial pH (r=0.52, P=0.0030, n=30), but not with umbilical cord arterial partial pressure of oxygen. The interclass correlation coefficient was 0.94.

CONCLUSIONS

Tissue oxygen saturation of the fetal head was obtained easily by the examiner's finger-mounted fetal tissue oximetry.

Evidence-based delivery room care of the very low birth weight infant

The first hour of a newborn's life is fraught with difficulty. Recommendations regarding the fundamental issues of resuscitation of these infants are developed and disseminated by the International Liaison Committee on Resuscitation and other organizations. However, these recommendations frequently do not address the needs of the very low birth weight infant and do not address some of the nuances that might lead to improved outcome. Improved organization and teamwork as well as improved monitoring and respiratory support can potentially improve the outcome of these infants.

Neonatal resuscitation for the preterm infant: evidence versus practice

In an effort to determine the actual conduct of neonatal resuscitation and the errors that may be occurring during this process, we developed a method of video recording neonatal resuscitations as an ongoing quality assurance project. We initiated video recordings of resuscitations using simple video recorders attached to an overhead warmer and reviewed the resultant tapes during biweekly quality improvement meetings. We also added the continuous recording of analog information such as heart rate, oximeter values, fraction of inspired oxygen and airway pressure. We subsequently developed a checklist that includes a preresuscitation briefing and a postresuscitation debriefing, all of which are reviewed at the same time as the video recording. We have examined the use of oxygen in the very preterm infant, the effectiveness of bag and mask ventilation, including the detection of airway obstruction during such ventilation, intubation in the delivery area and environment. In addition, we have trained our teams and leaders using Crew Resource Management and focused on improved communication. The availability of a dedicated room for resuscitation allows an increased ambient environment and the ability to provide a user-friendly setting similar to the neonatal intensive care unit to optimize performance. There are numerous opportunities for improving team and leader performance and outcomes following neonatal resuscitation. Further prospective studies are required to evaluate specific interventions.

Oxygen saturation monitoring for the preterm infant: the evidence basis for current practice

Many of the morbid conditions associated with extreme immaturity are potentiated by an excess of free radicals occurring in infants who developmentally have decreased levels of antioxidants. The optimal oxygen saturation values for the resuscitation, stabilization, and ongoing care of the very low birth weight infant remain largely undefined. We have reviewed the currently available evidence for clinical oxygen use in the newborn period. Until the results of further studies are available, a reasonable approach to resuscitation would include initial resuscitation with 30-40% oxygen for very preterm infants using targeted SpO2 values and blended oxygen during the first 10 min. For ongoing management of preterm infants, SpO2 targets of 85-93% seem to be most appropriate, with alarm limits set within 1 to 2% of these targets with intermittent audits to ensure compliance. There is no strong evidence to support the use of altered limits for the infant who develops early evidence of retinopathy of prematurity. Further prospective studies are required to evaluate the effects of varied oxygen targets on long-term outcome.

Fetal acidosis from obstetric interventions during the first vaginal delivery

OBJECTIVE

The aim of this study was to analyze the blood gas values of umbilical cord blood in newborns of first vaginal deliveries with or without obstetric interventions.

MATERIALS AND METHODS

In a prospective descriptive study conducted during the 6-month period from August 2003 through February 2004 at a university hospital, we analyzed the umbilical cord blood gas results of 80 term newborns delivered vaginally from healthy nulliparous women. Multivariate logistic analysis was used to evaluate the associations between fetal acidosis (pH<7.20) and any obstetric interventions.

RESULTS

The mean of umbilical cord blood arterial pH was 7.26 (standard deviation, 0.072). After controlling for the confounding factors with multivariate logistic regression, fetal acidosis (pH<7.20) was found to be significantly associated with oxytocin augmentation (odds ratio [OR], 16.48; 95% confidence interval [CI], 1.21-226.1) and vacuum extraction (OR, 10.76; 95% CI, 1.025-112.9). In contrast, there was no significant relationship between fetal acidosis with episiotomy (OR, 1.096; 95% CI, 0.07-16.6) or epidural anesthesia (OR, 0.074; 95% CI, 0.003-2.09).

CONCLUSION

Oxytocin augmentation and vacuum extraction were significantly related to low cord arterial pH values (pH<7.20), but there were no adverse effects to the newborns of first vaginal deliveries.

Fetal pulse oximetry: correlation with intrapartum fetal heart rate patterns and neonatal outcome

AIM

To determine how fetal pulse oximetry behaves in various cardiotocographic (CTG) tracings and correlates with neonatal outcome.

PATIENTS AND METHODS

Pregnant women undergoing active labor with singleton pregnancies of 32-42 weeks were enrolled. CTG recordings were reassuring or nonreassuring (namely variable or persisting late decelerations). Pulse oximetry values during labor and changing throughout deceleration and recovery phases, duration and frequency of pulse oximetry recordings <30%, and neonatal outcome were determined. One-way anova, Tukey test, chi(2)-test and multiple logistic regression model were used for statistical analysis where appropriate.

RESULTS

A total of 156 pregnant subjects were divided into three groups: reassuring fetal heart rate (FHR) patterns (group 1, n=78 [50%]), late decelerations (group 2, n=16 [10.3%]) and variable decelerations (group 3, n=62 [39.7%]). The initial and final pulse oximetry readings, pulse values in first stage of labor, the duration and the frequency of pulse oximetry recordings <30% were significantly different between groups (P<0.001, P<0.001, P<0.001, P=0.001, P<0.001). Fetal acidosis was significantly more frequent with late decelerations (23.1%, P=0.004). A multiple logistic regression model demonstrated that the initial pulse oximetry value during active labor was the most predictive variable of neonatal well-being (P<0.001).

CONCLUSION

Decreased fetal pulse oximetry values, especially prolonged and recurrent recordings <30% are well-correlated with abnormal FHR patterns, indicating an association with fetal compromise and metabolic acidosis. Going through active labor with a lower initial value of FSpO(2) more frequently leads to an altered FHR pattern and subsequent adverse fetal outcome.

[Fetal pulse oximetry: clinical practice]

OBJECTIVE

To assess in current practice the application of our protocol of using fetal pulse oximetry during labor, to evaluate whether fetal scalp blood sampling can be reduced and to determinate reliability of fetal pulse oximetry on the prediction of poor neonatal outcomes.

STUDY DESIGN

Prospective observational unicenter cohort including 449 patients during two years. All pregnancies were singleton, greater than or equal to 37 weeks' gestation, cephalic presentation, and had non reassuring fetal heart rate. The poor neonatal outcome was defined by one of the followings: arterial umbilical cord pH<or=7.15, umbilical cord base deficit greater than or equal to 12 mmol/l, 5 min Apgar score less than or equal to 7, transfer in neonatal intensive care unit, secondary respiratory distress and death.

RESULTS

The use of fetal pulse oximetry was concordant with our protocol in more than 80% of cases. The frequency of fetal scalp blood sampling was significantly reduced from 9.9 to 8.6% after the introduction of our protocol. With a 30% threshold, diagnostical values of fetal oximetry for a poor neonatal outcome were 9.1% for sensitivity, 93.1% for specificity, 79.4% for negative predictive value and 25.9% for positive predictive value. With a 40% threshold, the diagnostic values were 74, 51.6, 88.2 and 28.9% respectively.

CONCLUSION

The strict application of our protocol allow a less aggressive management of labor with a significant decrease in fetal scalp blood sampling. This study shows that with a 40% threshold, fetal pulse oximetry could be considered as a reliable tool for the management of labor with no increase of poor neonatal outcomes. On the other hand, the threshold which could determine whether an abnormal fetal heart rate needs immediate intervention still remains unclear.

Resuscitation of preterm neonates by using room air or 100% oxygen

OBJECTIVE

In this study of preterm neonates of <32 weeks, we prospectively compared the use of room air versus 100% oxygen as the initial resuscitation gas.

METHODS

A 2-center, prospective, randomized, controlled trial of neonates with gestational ages of 23 to 32 weeks who required resuscitation was performed. The oxygen group was initially resuscitated with 100% oxygen, with decreases in the fraction of inspired oxygen after 5 minutes of life if pulse oxygen saturation was >95%. The room air group was initially resuscitated with 21% oxygen, which was increased to 100% oxygen if compressions were performed or if the heart rate was <100 beats per minute at 2 minutes of life. Oxygen was increased in 25% increments if pulse oxygen saturation was <70% at 3 minutes of life or <80% at 5 minutes of life.

RESULTS

Twenty-three infants in the oxygen group (mean gestational age: 27.6 weeks; range: 24-31 weeks; mean birth weight: 1013 g; range: 495-2309 g) and 18 in the room air group (mean gestational age: 28 weeks; range: 25-31 weeks; mean birth weight: 1091 g; range: 555-1840 g) were evaluated. Every resuscitated patient in the room air group met rescue criteria and received an increase in the fraction of inspired oxygen by 3 minutes of life, 6 patients directly to 100% and 12 with incremental increases. Pulse oxygen saturation was significantly lower in the room air group from 2 to 10 minutes (pulse oxygen saturation at 3 minutes: 55% in the room air group vs 87% in the oxygen group). Heart rates did not differ between groups in the first 10 minutes of life, and there were no differences in secondary outcomes.

CONCLUSIONS

Resuscitation with room air failed to achieve our target oxygen saturation by 3 minutes of life, and we recommend that it not be used for preterm neonates.

Intrapartum Assessment of the Fetus: Historical and Evidence-Based Practice

The principal purpose of intrapartum fetal assessment is to detect hypoxemia-ischemia, which may lead to fetal jeopardy. A quarter century ago, electronic fetal monitoring replaced intermittent auscultation as the primary method of intrapartum fetal assessment in the United States. It seems that electronic fetal monitoring will continue to be the primary mode of intrapartum fetal assessment, with intermittent auscultation used in some centers primarily for low-risk parturients. From this abridged history of intrapartum fetal monitoring, it is recognized that all surveillance methods bear inherent limitations.

Effects of ephedrine and phenylephrine on uterine and placental circulations and fetal outcome following fetal hypoxaemia and epidural-induced hypotension in a sheep model †

BACKGROUND

Recent studies support the use of alpha-agonists during regional anaesthesia in uncomplicated term pregnancies. We hypothesized that ephedrine and phenylephrine, administered for maternal hypotension following fetal hypoxaemia, are equal in respect of fetal outcome.

METHODS

At 117-132 days gestation, chronically instrumented, anaesthetized and mechanically ventilated ewes were randomized to receive boluses of ephedrine (n=9) or phenylephrine (n=8) for maternal epidural-induced hypotension after a period of fetal hypoxaemia. Uterine (QUtA) and placental (QUA) volume blood flows were measured with perivascular transit-time ultrasonic flow probes, and uterine (RUtA) and placental (RUA) vascular resistances were computed from volume blood flows and maternal and fetal mean arterial pressures. Uterine (PIUtA) and umbilical artery (PIUA) pulsatility indices were obtained by Doppler ultrasonography.

RESULTS

Ephedrine increased QUtA and decreased RUtA and PIUtA from a hypotensive to baseline level and had no significant effect on umbilical circulation. With phenylephrine, QUtA remained lower (P=0.011) and RUtA higher (P=0.043) than at baseline, although PIUtA decreased to baseline level. PIUA increased from baseline with phenylephrine (P=0.007), whereas QUA decreased (P=0.050). Maternal volume expansion with hydroxyethyl starch decreased RUtA significantly irrespective of the vasopressor used. There were no significant differences in fetal blood gas values or lactate concentrations between the ephedrine and phenylephrine groups.

CONCLUSIONS

Despite the more favourable effects on uterine and placental circulations of ephedrine over phenylephrine, no significant differences in fetal acid-base status or lactate concentrations were observed.

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

OBJECTIVE

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

RESULTS

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

CONCLUSION

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

Developmental regulation of prostaglandin E2 synthase in porcine ductus arteriosus

The synthesis of PGE2, the major vasodilator prostanoid of the ductus arteriosus (DA), is catalyzed by PGE2 synthases (PGES). The factors implicated in increased PGE2 synthesis in the perinatal DA are not known. We studied the developmental changes of PGES along with that of cyclooxygenase (COX)-2 and cytosolic phospholipase A2 (cPLA2) in the DA of fetal (75-90% gestation) and immediately postnatal newborn (NB) piglets. Levels of microsomal PGES (mPGES), COX-2, and PGE2 in the DA of NB were ∼7-fold higher than in fetus; activities of cytosolic PGES (cPGES) and cPLA2 in DA of the fetus and NB did not differ. Because platelet-activating factor (PAF) could regulate COX-2 expression, the former was measured and found to be more abundant in the DA of the NB than of fetus. PAF elicited an increase in mPGES, COX-2, and PGE2 in fetal DA to levels approaching those of the NB; cPGES, cPLA2, and COX-1 were unaffected. In perinatal NB DA, PAF receptor antagonists BN-52021 and THG-315 reduced mPGES, COX-2, and PGE2 levels and were associated with increased DA tone. It is concluded that PAF contributes in regulating DA tone by governing mPGES, COX-2, and ensuing PGE2 levels in the perinate.

The influence of vacuum extractor on fetal oxygenation and newborn status

AIM

The aim of this study was to determine the effects of vacuum extractor assisted delivery on fetal oxygenation and acid-base balance.

METHODS

Sixty-one women were enrolled in the present study. The subjects were divided into two groups. Group A, consisting of 39 women, had normal vaginal deliveries. Group B, consisting of 22 women, underwent a vacuum extractor assisted vaginal delivery. Fetal arterial oxygen saturation (SpO2) monitoring was used in all women after full cervical dilatation. After delivery, umbilical artery pH, pCO2, pO2 and base deficit (BDecf) levels were determined in all neonates.

RESULTS

The mean FSpO2 value in Group A was 51.53+/-5.87% and in Group B 48.03+/-6.39% (p<0.03). The mean cord pH value in fetuses of Group A was 7.26+/-0.05, and in Group B 7.17+/-0.09. There was also a significant difference between the two groups with regards to mean pO2, pCO2 and BDecf values.

CONCLUSIONS

Vacuum assisted vaginal delivery was associated with lower fetal arterial oxygen saturation levels as well as lower cord blood pH values compared to those seen after unassisted vaginal delivery. Although decreased, however, the above parameters remained within normal ranges.

Cerebral hemoglobin concentration and oxygen saturation measured by intensity modulated optical spectroscopy in the human fetus during labor

AIMS

To quantify hemoglobin concentration and oxygen saturation in the human fetal brain using intensity modulated optical spectroscopy during labor.

METHODS

A specially designed probe was applied to the fetal scalp in 20 women during uncomplicated labor at term. Optical fibres transmitted near infra-red light to and from an intensity modulated optical spectrometer (IMOS), which detected changes in the optical parameters of the infra-red light source. Using novel off-line analytic techniques, these changes were converted into absolute measurements of oxyhemoglobin (HbO2) and deoxyhemoglobin (Hb). Summing Hb and HbO2 gives total hemoglobin concentration (HbT) and HbO2/HbT x 100% provided measurements of cerebral saturation (SmcO2).

RESULTS

Of 20 fetuses studied, data from 10 fetuses were suitable for analysis. Over three consecutive uterine contractions, the mean (+/- SD) absolute cerebral concentrations of Hb and HbO2 were 30 +/- 18 and 46 +/- 21 mumol/l, respectively. This gave a mean cerebral HbT of 77 +/- 29 mumol/l and a mean SmcO2 of 59 +/- 12%. In the other ten fetuses insufficient light was detected to allow chromophore quantification.

CONCLUSION

These are the first absolute measurements of cerebral Hb and HbO2 in human fetuses during labor. The values of total hemoglobin are similar to those obtained in neonates with hypoxia-ischemia and the measurements of fetal cerebral oxygen saturation are similar to previously published values.

Evaluation of non-reassuring fetal heart rate patterns with fetal pulse oximetry combined with vibratory acoustic stimulation

OBJECTIVE

To determine the value of fetal pulse oximetry and vibratory acoustic stimulation in the presence of non-reassuring fetal heart rate patterns during labor.

DESIGN

Prospective study in women monitored by cardiotocography and fetal pulse oximetry during labor.

MATERIALS AND METHODS

During a period of 18 months, 907 consecutive parturients in labor were monitored by cardiotocography. Out of these women, 63 were selected on the basis of a non-reassuring fetal heart rate tracing during the first stage of labor. In these cases, fetal pulse oximetry was applied. Vibratory acoustic stimulation was applied in fetuses without spontaneous reactivity in order to evaluate the fetal status.

RESULTS

Our cases were classified into three groups, according to the lower fetal oxygen saturation levels, from the time of oximetry application until delivery. Group A consisted of 29 cases where fetal oxygen saturation levels were > or = 41%, group B (20 cases) with fetal oxygen saturation of 31-40% and group C (14 cases) with levels of < 30%. Spontaneous reactivity was observed in 15 fetuses of group A and seven of group B, while no case of reactivity was noted in group C. Vibratory acoustic-induced reactivity was associated with low fetal oxygen saturation levels. The mean umbilical artery pH levels were 7.29 +/- 0.051 in group A, 7.21 +/- 0.057 in group B and 7.04 +/- 0.05 in group C.

CONCLUSION

Fetal pulse oximetry should be indicated not only in fetuses without any reactivity but also in those with induced reactivity, after the application of vibratory acoustic stimulation.

Airway management on placental support (AMPS)--the anaesthetic perspective

Neonatal airway obstruction has been reported to have a high mortality. Antenatal diagnosis of this condition is now possible. Anaesthetic and surgical techniques have been developed that allow neonatal airway obstruction to be managed at delivery, while the fetus remains oxygenated via the placental circulation. Three case studies are presented, and the anaesthetic issues for mother and fetus/neonate are discussed with reference to previously published cases of airway management on placental support. In particular, techniques for uterine relaxation and maintenance of placental circulation are explored. The history of these procedures and issues of planning and logistics are also discussed.

Abnormal fetal heart rate patterns during the active phase of labor: the value of fetal oxygen saturation

OBJECTIVE

To determine the predictive value of intrapartum fetal oxygen saturation (SO2) for prediction of an umbilical artery pH less than 7.15 at birth in labors complicated by abnormal fetal heart rate traces.

STUDY DESIGN

Eighty-five primigravidas in spontaneous labor complicated by abnormal fetal heart rate traces underwent fetal SO2 monitoring using the fetal pulse oximetry technique. Cases with an SO2 of < 30% were delivered by Cesarean section. Umbilical artery pH was measured at birth in all women.

RESULTS

With the value set of 30% as the cut-off point of fetal oxygen saturation, the positive predictive value for umbilical artery pH of < 7.15 was 61.5% and the negative predictive value was 95.8%, with a sensitivity of 72% and a specificity of 93%.

CONCLUSIONS

Fetal pulse oximetry is a promising technique for assessment of fetal well-being during labor and may decrease the number of unnecessary Cesarean sections.

Intrapartum cardiotocography and fetal pulse oximetry in assessing fetal hypoxia

OBJECTIVES

A retrospective analysis of short-term variability (STV), a cardiotocography (CTG) parameter, in relation to fetal blood saturation values (FSpO(2)) obtained by fetal pulse oximetry.

METHODS

The study included 26 healthy pregnant women monitored continuously during delivery with both cardiotocography and fetal pulse oximetry.

RESULTS

Lower FSpO(2) values were observed in the group showing STV levels <or=6.0 ms in the 1st stage of labor (44.7+/-3.46% vs. 49.2+/-1.8%), but this result was not statistically significant. In the 2nd stage of labor, FSpO(2) values in the group with STV levels <or=6.0 ms were significantly lower than those with STV levels >6.0 ms (34.4+/-2.9% vs. 43+/-7.2%; P<0.001). A positive correlation was found between STV levels <or=6.0 ms and mean FSpO(2) values in the 2nd stage of labor.

CONCLUSIONS

1. A significant relationship was observed between short-term variability in the cardiotocographic records and fetal blood saturation levels in the 2nd stage of labor. 2. Fetal pulse oximetry can be valuable in assessing fetal wellbeing, especially when CTG records are abnormal.

The future of intrapartum fetal pulse oximetry

Fetal pulse oximetry has undergone a remarkable evolution since its conception over 10 years ago. A number of important observations, including the recent publication of a large randomized clinical trial, have provided further insight into our understanding of intrapartum fetal physiology and intrapartum fetal assessment. The purpose of this paper is to review significant developments in this technology over the past 2 years and to propose paths for future clinical research.

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

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

CONCLUSION

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

A multicenter controlled trial of fetal pulse oximetry in the intrapartum management of nonreassuring fetal heart rate patterns

OBJECTIVE

Recent developments permit the use of pulse oximetry to evaluate fetal oxygenation in labor. We tested the hypothesis that the addition of fetal pulse oximetry in the evaluation of abnormal fetal heart rate patterns in labor improves the accuracy of fetal assessment and allows safe reduction of cesarean deliveries performed because of nonreassuring fetal status.

STUDY DESIGN

A randomized, controlled trial was conducted concurrently in 9 centers. The patients had term pregnancies and were in active labor when abnormal fetal heart rate patterns developed. The patients were randomized to electronic fetal heart rate monitoring alone (control group) or to the combination of electronic fetal monitoring and continuous fetal pulse oximetry (study group). The primary outcome was a reduction in cesarean deliveries for nonreassuring fetal status as a measure of improved accuracy of assessment of fetal oxygenation.

RESULTS

A total of 1010 patients were randomized, 502 to the control group and 508 to the study group. There was a reduction of >50% in the number of cesarean deliveries performed because of nonreassuring fetal status in the study group (study, 4. 5%; vs. control, 10.2%; P =.007). However, there was no net difference in overall cesarean delivery rates (study, n = 147 [29%]; vs. control, 130 [26%]; P = .49) because of an increase in cesarean deliveries performed because of dystocia in the study group. In a blinded partogram analysis 89% of the study patients and 91% of the control patients who had a cesarean delivery because of dystocia met defined criteria for actual dystocia. There was no difference between the 2 groups in adverse maternal or neonatal outcomes. In terms of the operative intervention for nonreassuring fetal status, there was an improvement in both the sensitivity and the specificity for the study group compared with the control group for the end points of metabolic acidosis and need for resuscitation.

CONCLUSION

The study confirmed its primary hypothesis of a safe reduction in cesarean deliveries performed because of nonreassuring fetal status. However, the addition of fetal pulse oximetry did not result in an overall reduction in cesarean deliveries. The increase in cesarean deliveries because of dystocia in the study group did appear to result from a well-documented arrest of labor. Fetal pulse oximetry improved the obstetrician's ability to more appropriately intervene by cesarean or operative vaginal delivery for fetuses who were actually depressed and acidotic. The unexpected increase in operative delivery for dystocia in the study group is of concern and remains to be explained.

Intrapartum fetal pulse oximetry. Part I: Principles and technical issues

Fetal pulse oximetry has been advocated as a means of improving the specificity of cardioto-cography in intrapartum fetal surveillance. The objective of this article, the first of two reviewing the current literature on fetal pulse oximetry, is to discuss the principles of this new and evolving technology, its development, and the various factors that can affect its readings during fetal monitoring. It serves as a prelude to the second article, which profiles the clinical application of fetal pulse oximetry. Literature pertaining to this topic was selected from a MEDLINE search from 1965 through September 1999, with additional sources obtained through cross-referencing.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians

LEARNING OBJECTIVES

After completion of this article, the reader will be able to explain the principles of fetal pulse oximetry, and describe the factors that affect the calibration of fetal pulse oximeters and the factors that affect the fetal pulse oximeter readings.

Umbilical cord blood gas analysis

Umbilical cord blood gas and pH values should always be obtained in the high-risk delivery and whenever newborn depression occurs. This practice is important because umbilical cord blood gas analysis may assist with clinical management and excludes the diagnosis of birth asphyxia in approximately 80% of depressed newborns at term. The most useful umbilical cord blood parameter is arterial pH. Sampling umbilical venous blood alone is not recommended because arterial blood is more representative of the fetal metabolic condition and because arterial acidemia may occur with a normal venous pH. A complete blood gas analysis may provide important information regarding the type and cause of acidemia and sampling the artery and vein may provide a more clear assessment. The sampling technique is simple and easily mastered by any treatment person in the delivery room. Preheparinized syringes ensure a consistent dose and amount of heparin. Depending on how normality is defined and on the population studied, normal ranges for umbilical cord blood gas values vary (see Table 1). In general, the lower range for normal arterial pH extends to at least 7.10 and that for venous pH to at least 7.20. Many different factors during pregnancy, labor, and delivery can affect cord blood gases. Umbilical blood sampling for acid-base status at all deliveries cannot be universally recommended because many facilities do not have the capabilities to support such a practice and in doing so may impose an excessive financial burden. Considering the costs, the accumulated published data, and the nonspecificity of electronic fetal monitoring in the evaluation of fetal oxygenation, it may be more rational to implement universal cord blood gas analysis. Care providers and institutions with the logistical capabilities in place should consider the cost efficacy of routine cord blood gas analysis because it is the gold standard assessment of uteroplacental function and fetal oxygenation/acid-base status at birth.