Fetal Pulse Oximetry Research Articles

Use of Fetal Pulse Oximetry Among High-Risk Women in Labor: A Randomized Clinical Trial

Use of Fetal Pulse Oximetry Among High-Risk Women in Labor: A Randomized Clinical Trial

The MFMU network randomized trial of fetal pulse oximetry

ObjectiveTo measure whether knowledge of fetal oxygen saturation, as an adjunct to continuous electronic fetal monitoring, (1) is associated with a significant change in the overall rate of cesarean delivery, including those performed specifically for non-reassuring fetal heart rate pattern and dystocia, and (2) is related to infant condition at birth.Study design5341 nulliparous women at term in early labor were randomly assigned to “open” or “masked” fetal pulse oximetry. In the “open” arm, fetal oxygen saturation values were displayed to the clinician. In the “masked” group, the fetal oxygen sensor was inserted and the values recorded by computer, but the data were hidden. Labors complicated by a non-reassuring fetal heart rate pattern prior to randomization were documented for subsequent analysis. The trial was stopped before the final sample size of 10,000 because the overall cesarean rate (primary outcome) in the masked arm was higher than expected, and there was >90% power to detect the prespecified 15% reduction in the open arm.ResultsTabled 1Outcome“Open” arm n = 2,629“Masked” arm n = 2,712P-valueCesarean Rate-Overall26.3%27.5%0.31Indication: Non-Reassuring FHR7.1%7.9%0.30 Dystocia18.6%19.2%0.59Forceps/Vacuum14.5%14.7%0.765-Minute Apgar: 7 or less2.9%3.2%0.55 3 or less0.2%0.1%0.34Newborn Seizures0.1%0.2%0.51HIE00.04%1.0Intrapartum Stillbirth00—Neonatal Death00.04%1.0 Open table in a new tab ConclusionKnowledge of fetal oxygen saturation is not associated with a reduction in the rate of cesarean delivery or improvement in newborn condition. ObjectiveTo measure whether knowledge of fetal oxygen saturation, as an adjunct to continuous electronic fetal monitoring, (1) is associated with a significant change in the overall rate of cesarean delivery, including those performed specifically for non-reassuring fetal heart rate pattern and dystocia, and (2) is related to infant condition at birth. To measure whether knowledge of fetal oxygen saturation, as an adjunct to continuous electronic fetal monitoring, (1) is associated with a significant change in the overall rate of cesarean delivery, including those performed specifically for non-reassuring fetal heart rate pattern and dystocia, and (2) is related to infant condition at birth. Study design5341 nulliparous women at term in early labor were randomly assigned to “open” or “masked” fetal pulse oximetry. In the “open” arm, fetal oxygen saturation values were displayed to the clinician. In the “masked” group, the fetal oxygen sensor was inserted and the values recorded by computer, but the data were hidden. Labors complicated by a non-reassuring fetal heart rate pattern prior to randomization were documented for subsequent analysis. The trial was stopped before the final sample size of 10,000 because the overall cesarean rate (primary outcome) in the masked arm was higher than expected, and there was >90% power to detect the prespecified 15% reduction in the open arm. 5341 nulliparous women at term in early labor were randomly assigned to “open” or “masked” fetal pulse oximetry. In the “open” arm, fetal oxygen saturation values were displayed to the clinician. In the “masked” group, the fetal oxygen sensor was inserted and the values recorded by computer, but the data were hidden. Labors complicated by a non-reassuring fetal heart rate pattern prior to randomization were documented for subsequent analysis. The trial was stopped before the final sample size of 10,000 because the overall cesarean rate (primary outcome) in the masked arm was higher than expected, and there was >90% power to detect the prespecified 15% reduction in the open arm. ResultsTabled 1Outcome“Open” arm n = 2,629“Masked” arm n = 2,712P-valueCesarean Rate-Overall26.3%27.5%0.31Indication: Non-Reassuring FHR7.1%7.9%0.30 Dystocia18.6%19.2%0.59Forceps/Vacuum14.5%14.7%0.765-Minute Apgar: 7 or less2.9%3.2%0.55 3 or less0.2%0.1%0.34Newborn Seizures0.1%0.2%0.51HIE00.04%1.0Intrapartum Stillbirth00—Neonatal Death00.04%1.0 Open table in a new tab ConclusionKnowledge of fetal oxygen saturation is not associated with a reduction in the rate of cesarean delivery or improvement in newborn condition. Knowledge of fetal oxygen saturation is not associated with a reduction in the rate of cesarean delivery or improvement in newborn condition.

Women's evaluations of their experience in a multicenter randomized controlled trial of intrapartum fetal pulse oximetry (the FOREMOST trial)

ObjectiveFetal pulse oximetry improves the assessment of fetal well being during labor. We evaluated women´s satisfaction with their experience with this additional technology.Study designWe surveyed women participating in the FOREMOST trial, a randomized controlled trial comparing the addition of fetal pulse oximetry (FPO) to conventional cardiotocograph (CTG) monitoring (intervention group), versus CTG-only (control group), in the presence of non-reassuring fetal status during labor. Our survey evaluated three aspects of women´s experience: fetal-monitoring, labor and participation in the research. The survey was administered within a few days of giving birth and repeated three months later.ResultsThere were no differences between the intervention and control groups for women´s evaluations of their labor, fetal monitoring, research or overall experiences, when surveyed on the two occasions. Within each study group, there was a small but statistically significant decline in women´s scores for their experience of labor and overall experience from the initial survey close to the time of giving birth, to three months later. The magnitude of differences in responses over time was similar for the two groups. Women were more satisfied following a spontaneous or assisted vaginal birth than following cesarean section (Survey 1 p < 0.001, Survey 2 p < 0.001). Length of time the research midwife was present had a significant positive effect on women´s ratings of their experience several days after giving birth (p=0.006) but no effect at three months.ConclusionThe addition of fetal pulse oximetry for the assessment of fetal well-being during labor did not affect childbearing women´s perceptions of fetal monitoring or their labor. Women evaluated their experience in the research process positively overall. There were small changes in women´s perception of their satisfaction over time.

The effect of maternal oxygen administration during labor on fetal pulse oximetry: A pilot study

The effect of maternal oxygen administration during labor on fetal pulse oximetry: A pilot study

A cost-effectiveness analysis of the intrapartum fetal pulse oximetry multicentre randomized controlled trial (the FOREMOST trial)

To report an economic analysis of the Australian intrapartum fetal pulse oximetry (FPO) multicentre randomized controlled trial (the FOREMOST trial), which examined whether adding FPO to conventional cardiotocographic (CTG) fetal monitoring (intervention group) was a cost-effective intervention in reducing the operative delivery rate for non-reassuring fetal status, compared to CTG alone (control group).

The effect of intrapartum fetal pulse oximetry, in the presence of a non-reassuring fetal heart rate pattern, on operative delivery rates: A multicenter randomized controlled trial (the FOREMOST trial)

The effect of intrapartum fetal pulse oximetry, in the presence of a non-reassuring fetal heart rate pattern, on operative delivery rates: A multicenter randomized controlled trial (the FOREMOST trial)

Fetal Pulse Oximetry and Neonatal Outcome: A Study in a Developing Country

The aim of this cohort, prospective study was to compare the diagnostic value of intrapartum fetal pulse oximetry (FPO) with that of fetal scalp blood gas (FSBG) for an abnormal neonatal outcome in cases with abnormal fetal heart rate (FHR) tracings. Fetal oxygen saturation was continuously monitored with Nellcor N-400 FPO during labor. Simultaneous FSBG determinations were obtained. The results were analyzed in relation to umbilical arterial cord blood pH and neonatal outcome. Studied FPO cutoff levels were 30 and 40% hemoglobin saturation and that of FSBG pH was 7.2. During the study, there were 9825 deliveries; 415 had abnormal FHR. Only 150 fulfilled the whole screening panel. When the outcome variable was umbilical arterial pH, the positive predictive values of the three methods (FPO30, FPO40, FSBG) were 57, 61 and 65% and the negative predictive values were 43, 39 and 35% respectively. The sensitivity of FPO30 was highest (75%). Considering abnormal neonatal outcome, again the sensitivity was also highest for FPO30 (89%). The sensitivity of FSBG was 82%. The specificity of the three methods were 53, 49 and 38% respectively. The diagnostic value of intrapartum FPO compares favorably with FSBG. FPO seems to be a reliable and less invasive tool and may decrease unnecessary interventions and unnecessary fetal scalp blood sampling in cases of suspected fetal distress. The FPO cutoff of 30% saturation defined by previous studies appears to be appropriate.

Use of fetal pulse oximetry among high-risk women in labor: A randomized clinical trial

The purpose of this study was to determine the clinical role of fetal pulse oximetry to reduce cesarean delivery for a nonreassuring fetal heart rate tracing. Singletons > or =28 weeks were randomized to fetal pulse oximetry plus electronic fetal heart rate monitoring (monitoring + fetal pulse oximetry) or monitoring alone. Overall, 360 women in labor were recruited: 150 cases with monitoring+fetal pulse oximetry and 177 cases with monitoring alone were analyzed. Most demographic, obstetric, and neonatal characteristics were similar. Specifically, the gestational age, cervical dilation, and station of the fetal head were not differential factors. In addition, cesarean delivery for nonreassuring fetal heart rate tracing was not different between the group with monitoring+fetal pulse oximetry (29%) and the group with monitoring alone (32%; relative risk, 0.95; 95% CI, 0.75, 1.22). Likewise, cesarean delivery for arrest disorder was similar between the group with monitoring+fetal pulse oximetry (22%) and the group with monitoring alone (23%; relative risk, 1.05; 95% CI, 0.79, 1.44). However, the decision-to-incision time was shorter for the group with monitoring+fetal pulse oximetry (17.8 +/- 8.2 min) than for the group with monitoring alone (27.7 +/- 13.9 min; P < .0001). The use of fetal pulse oximetry with electronic fetal heart rate monitoring does not decrease the rate of cesarean delivery, although it does alter the decision-to-incision time.

Alterations in Doppler velocimetry indices of the umbilical artery during fetal hypoxia in labor, in relation to cardiotocography and fetal pulse oximetry findings

The aim was to investigate fetal peripheral blood flow using external cardiotocography (CTG), Doppler velocimetry, and pulse oximetry (PO) in normal labor compared with those complicated by hypoxia. During labor, 35 term fetuses with oxygen saturation values (FSPO(2)) between 30 and 40%, and 25 term fetuses with FSPO(2) values < or =30% for a period of 20 s to 2 min were studied. Fetuses were assessed using simultaneous CTG, PO, and Doppler ultrasonography of the umbilical artery (UA). The pulsatility index (PI), resistance index (RI), and flow velocity integral (FVI) were recorded. Peripartum outcomes were compared with those of 30 fetuses with SPO(2) values >40%. All groups presented abnormal CTG patterns and were comparable with regard to maternal age and parity. The Fetal Surveillance Unit of the 2nd Department of Obstetrics and Gynecology, "Aretaieion" Hospital, Athens University, Greece. Umbilical artery Doppler revealed an initial increase in the RI and the PI in the presence of decreased oxygen saturation. The differences observed in Doppler velocity and impedance indices correlated with PO values. Fetal outcomes correlated with UA Doppler findings. Alterations in UA Doppler velocimetry indices were observed during labor-induced fetal hypoxia. PO readings of <40% provoked an increase in the RI and PI. When PO readings remained <30% for >2 min, both the PI and the RI were further increased in a more prominent way. UA velocimetry indices correlated with perinatal outcome.

Die Zuverlässigkeit der fetalen Pulsoxymetrie bei der Detektion einer fetalen Azidose

Fetal pulse oximetry is a continuous method to exclude the lack of oxygen in cases of non-reassuring fetal heart rate. This study aims at the evaluation of the predictive value of this method concerning the development of fetal acidosis. 136 fetuses with non-reassuring heart rate were monitored by fetal pulse oximetry. In all cases fetal blood pH and base excess were determined repeatedly by fetal blood analysis (FBA). The pH value and base excess in the umbilical artery and scalp blood as well as the changes of pH and base excess were correlated to the duration of low, medium and high fetal oxygen saturation (FSpO (2)). Sensitivity, specificity, positive and negative predictive values were calculated for the assumption that "FSpO (2) < or = 30 % for at least 10 or 15 minutes" predicts a pH or base excess in the umbilical artery and in FBA of < 7.1/7.15/7.2 or < or = -4/8/12 mmol/L and a decline of pH (base excess) by more than 0.05 (0.1) pH units (4 mmol/L). A highly significant negative correlation was found between umbilical artery and FBA pH and base excess as well as the change of both and the duration of low oxygen saturation. Additionally the change of FBA pH depends on the duration of medium FSpO (2). A pH below 7.15 in FBA as well as base excess < or = -12 mmol/L were safely detected by a cut-off of "FSpO (2) < or = 30 % for at least 10 minutes" and pH < 7.1 and base excess < or = -12 mmol/l in FBA in 100 % and 75 %, respectively. A decline of pH by more than 0.1 pH units and of base excess by more than 4 mmol/L were excluded by a negative predictive value of 98 %. In conclusion, medium and progressive acidosis can be reliably excluded by fetal pulse oximetry.

Transabdominal fetal pulse oximetry with near-infrared spectroscopy

The purpose of this study was to determine the feasibility of noninvasive fetal pulse oximetry in the human fetus with transabdominal continuous-wave near-infrared spectroscopy. The instrument has 3 wavelength light-emitting diodes (735, 805, and 850 nm) as light sources and a photomultiplier tube as a detector. This instrument was used in 6 pregnant women (>36 weeks of gestation). First, a fetal heart rate was obtained with a fetal heart rate monitor. Then, the depth of fetal tissue (head) from the maternal abdomen was determined by ultrasound examination; the distance between the optodes (light source and the detector) was set to be approximately twice the depth of the fetus (7-11 cm). The data analysis was based on the modified Beer-Lambert law and the use of optical densities at 735 and 850 nm to obtain the concentration changes of the oxyhemoglobin and deoxyhemoglobin. The saturation was expressed as the percent of oxygen saturation equal to 100 x oxyhemoglobin/(oxyhemoglobin + deoxyhemoglobin). We recorded the spectroscopy data and the fetal heart rate for approximately 3 to 10 minutes in each patient. The mean oxygen saturation values of each of the 6 individual fetuses ranged from 50% to 74% (overall mean saturation, 61% +/- 14.8% [SD]). This preliminary data indicate that transabdominal fetal pulse oximetry is feasible for human patient application. The measured values were similar to those that are obtained with transvaginal pulse oximetry. Future studies should correlate transabdominally obtained measurements with those measurements that are obtained by transvaginal fetal pulse oximetry.

Severe Variable Decelerations and Fetal Pulse Oximetry during the Second Stage of Labor

Objectives: The aim of the study was to investigate the usefulness of fetal pulse oximetry in cases of severe variable decelerations in the second stage of labor. Methods: It is a prospective study including 58 patients. Thirty-eight patients (group A) had a normal uncomplicated labor and 20 patients (group B) developed severe variable decelerations during the second stage of labor. All patients were primiparous with normal pregnancies and had electronic fetal monitoring of labor in conjunction with fetal pulse oximetry. An estimation of fetal pH and base deficit was performed at delivery in all patients. Results: There was no statistically significant difference in relation to maternal age and gestational age between the two groups. Group A patients did not delivered neonates with metabolic acidosis. Six out of 20 (group B) patients delivered neonates with a pH <7.10 despite a fetal pulse oximetry reading of >30%. Conclusions: It appears that fetal pulse oximetry is not capable of detecting pre-acidotic or acidotic fetuses during the second stage of labor in patients with severe variable decelerations and the management of such patients should be supported by fetal scalp pH when indicated or otherwise the obstetrician should expedite delivery either with assisted operative delivery or cesarean section. Fetal heart rate monitoring was introduced into clinical practice over 30 years ago. It continues to be the predominant method of intrapartum fetal surveillance despite worries about its accuracy and efficacy.

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.

The pulse in reflectance pulse oximetry: Modeling and experimental studies

Reflectance pulse oximetry permits the use of alternative monitoring sites such as the face or torso, and is the approach commonly employed in fetal pulse oximetry systems. The purpose of this study is to investigate the impact of assumptions about the nature of arterial pulsatility on the calibration of such systems. Monte Carlo simulations of reflectance pulse oximetry were run on a six-layer tissue model, varying depth and magnitude of the arterial pulse. SpO2 readings on and off the femoral artery obtained during desaturation studies in newborn piglets were compared to predictions. Results. Monte Carlo simulation results clarified the difference between deep and shallow pulsatility found with photon diffusion models, agreeing with earlier in vivo observations. Significant overestimation of SpO2 <75% and slight underestimation >75% is expected if a sensor is placed on a highly pulsatile site. The on- and off-artery SpO2 readings recorded during desaturation in the newborn piglet follow the model predictions. The sensitivity of reflectance pulse oximetry calibration to the depth and magnitude of arterial pulsatility reinforces the observation that monitoring site selection is of importance in optimizing reflectance pulse oximetry performance, particularly fetal pulse oximetry. Sites with palpable pulsatility should be avoided.

Accuracy of Clinical Diagnosis of Fetal Distress

Background: Fetal distress has significantly contributed to the rising caesarean section rate, which is as high as 20?25%. Caesarean section for clinically diagnosed fetal distress has been criticized as being unjustified in many instances. Objectives: To assess the fetal outcome in women delivered by caesarean section following a clinical diagnosis of fetal distress and to determine the accuracy of this diagnosis. Methods: A retrospective analysis of the case notes of 126 parturients delivered by caesarean section for clinically diagnosed fetal distress at the University of Nigeria Teaching Hospital (UNTH) Enugu over a two?year period. Results: Forty six (36.5%) babies had Apgar scores of 7 and above, while 80(63.5%) had Apgar scores lower than 7, including 5 (4.0%) fresh stillbirths. The caesarean section rate in the hospital during the period covered by this study was 19.9% and fetal distress contributed 2.3% of this rate. The perinatal mortality rate was 39. 7 per 1000. Conclusion: Clinical diagnosis of fetal distress is accurate in about two?thirds of cases and wrong in the remaining one?third. Electronic fetal heart monitoring, fetal scalp blood sampling and fetal pulse oximetry should be provided by health care managers to improve diagnosis of fetal distress and minimize unnecessary caesarean sections. Though this study demonstrates the limitations of using clinical parameters alone in the diagnosis of fetal distress and in the selection of cases for caesarean section; however, in the absence of such modem facilities, clinical diagnosis is still useful, otherwise about two?thirds of such babies might perish. Key Words: Caesarean section, Fetal distress, Clinical diagnosis. Journal of College of Medicine Vol.9(1) 2004: 12-13

Erste Ergebnisse einer Pilotstudie mit dem FetalSAT Pulsoxymetriesystem

Einführung/Fragestellung: Ziel dieser Studie ist es, die Funktionsfähigkeit und Handhabung eines industriell gefertigten fetalen Pulsoxymetriesensors sowie eines an die üblichen CTG-Geräte adaptierbaren Auswertesystems (FetalSAT)™ zu prüfen.

Dystocia in nulliparous patients monitored with fetal pulse oximetry

Objective A critical analysis of the United States randomized controlled trial of fetal pulse oximetry concluded that nonreassuring fetal heart rate patterns used for study entry may have been a marker for dystocia. We prospectively studied nulliparous women in labor whose progress was monitored with fetal pulse oximetry to examine the relationship between nonreassuring fetal heart rate patterns and operative delivery for dystocia. Study design A prospective nonrandomized observational cohort study compared two distinct classes of nonreassuring fetal heart rate patterns (class I: intermittent, mildly nonreassuring; class II: persistent, progressive, and moderate to severely nonreassuring) among nulliparous patients with the use of fetal pulse oximetry to confirm fetal well-being. Definitions of dystocia included the cessation of labor progress in the first (3 hours) or second (2 hours) stage of labor, despite adequate uterine activity that was assessed with an intrauterine pressure catheter. Independent review confirmed the classification of nonreassuring fetal heart rate patterns and study entry criteria. Results Two hundred seventy-four patients met study criteria and had sufficient information for fetal heart rate tracing interpretation. Two hundred thirty-seven patients (86.5%) were class II, and 37 patients (13.5%) were class I. The two classes of patients were comparable in a variety of obstetric, demographic, and perinatal variables. Twelve percent of all patients were delivered for nonreassuring fetal status. Significantly more class II patients (22%) were delivered by cesarean for dystocia than were class I patients (8%). Higher doses and a longer number of hours of oxytocin were required among class II patients. Significantly more occiput posterior positions were noted among all patients who underwent cesarean delivery for dystocia compared with other modes of delivery. Conclusion Significantly nonreassuring fetal heart rate patterns predict cesarean delivery for dystocia among nulliparous patients with normally oxygenated fetuses in a setting of a standardized labor management protocol. This confirms the observations in the randomized controlled trial of fetal pulse oximetry in the United States and may provide insight into the treatment of nonprogressive labor in contemporary practice.

Evaluation of fetal intrapartum hypoxia by middle cerebral and umbilical artery Doppler velocimetry with simultaneous cardiotocography and pulse oximetry.

To investigate fetal circulation at different stages of hypoxia during labor, and to study blood flow alterations in the brain and peripheral tissues, through simultaneous use of three non-invasive techniques. Ninety two pregnant women between 38 and 41 weeks of gestation, comparable for maternal age and parity, were simultaneously monitored with cardiotocography (CTG), continuous fetal pulse oximetry and Doppler ultrasonography during the first stage of labor. In 70 cases evaluation was successful, and useful data was obtained. Doppler waveforms were obtained before and during abnormal CTG patterns, of both the umbilical (UA) and middle cerebral artery (MCA) to measure the pulsatility index (PI), resistance index (RI), and flow velocity integral (FVI). The study population was divided in three groups, according to CTG and fetal pulse oximetry tracings: 20 term fetuses with normal CTG patterns and oxygen saturation (FSPO(2)) values >40%, 30 term fetuses with abnormal CTG patterns and FSPO(2) values between 30 and 40%, and 20 fetuses with abnormal CTG patterns and FSPO(2) values <30% for a time up to 2 min. These were studied and peripartum outcomes were compared. Redistribution of blood flow was noted at FSPO(2) values of 37%, in all groups. In the presence of reduced oxygen saturation (near to or below 30%), MCA Doppler showed significantly lower PI (1.06+/-0.33 vs.0.74+/-0.39, p=0.03) and RI (0.59+/-0.14 vs. 0.44+/-0.14, p=0.03), while that of the UA showed mildly higher resistance indices (0.98+/-0.14 vs. 1.28+/-0.50, p=0.01 and 0.57+/-0.12 vs. 0.79+/-0.24, p=0.004, respectively). When an oxygen saturation value of <30% was maintained for greater than 2 min, MCA Doppler indices reversed, likely indicating morbid fetal hypoxia. Differences in fetal outcomes between groups correlated with Doppler and pulse oximetry tracings. During active labor the fetus maintains oxygen supply to the brain by redistributing blood flow. In cases of hypoxia this is feasible for only 2 min. We note a strong correlation between fetal pulse oximetry, Doppler velocimetry of the MCA and UA, and fetal morbidity.

European experience with a novel noninvasive sensor for intra-amniotic or extra-amniotic evaluation of fetal oxygen saturation.

We evaluated the feasibility of a new instrument for continuous fetal pulse oximetry during labor. The measuring sensor can be placed on the fetal back before or after rupture of membranes. One hundred adult women who had completed 32 weeks of gestation and had an anticipated duration of labor greater than 30 minutes were included in the study. Patients with premature rupture of membranes for 24 hours or more, low placental localization, placenta previa or abruption, vaginal bleeding, acute infection, polyhydramnios, oligohydramnios, or uterine or congenital abnormalities were excluded. All sensors were placed successfully. The mean continuous recording time was 276 minutes. Peripheral oxygen saturation as measured by pulse oximeter values were obtained during a median of 64.05% of the recording time. No chorioamnionitis or endometritis was noted. The new sensor instrumentation was safe for mother and fetus and was well accepted by parents and physicians.

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

Objective: Purpose of this presentation is to show the diagnostic power of fetal pulse oximetry in comparison to the other blood gas parameters from fetal blood samplings (FBS). The distribution of saturation readings in acidotic fetuses and normally oxygenated fetuses should be established. Study design: A fetal pulse oximetry system (N400, FS14) was evaluated in a strictly observational study design based on blinded saturation display and on continuous data storing. The investigation was performed on 170 fetuses with non-reassuring fetal heart rate (FHR)-tracings. Since pulse oximetry readings were not available for decision finding, the clinical management was based on electronic fetal monitoring and fetal blood samplings. The oxygen saturation from FBS or umbilical cord blood was measured by blood gas analysers with an integrated hemoximeter (Bayer 865; ABL 625, Radiometer) and biosensors measuring lactate as metabolic component. Out of the 170 cases 17 cases were defined as group of acidemia ( pH umb. art. < 7.16 + BD<−9.4). The distribution of saturation readings and the duration of desaturation periods (in minutes and percentage of total monitoring time SPO 2 below 30%) were determined. ROC curve analysis from FBS preceding delivery compared the diagnostic power of other blood gas parameters with oxygen saturation. The Wilcoxon test for uneven pairs was used. Results: The distribution of oxygen saturation in the normal group of fetuses differs significantly from the acidemic group. The correlation coefficient between both methods to determine oxygen saturation was r=0.66. A specific evaluation of the distribution of SPO 2 shows an overestimation of pulse oximetry in the low range and an underestimation in the high range of saturation. ROC-curve analysis showed a good diagnostic power of lactate in comparison to the oxygen saturation measured by pulse oximetry or by hemoximetry. Conclusions: The advantage of continuous fetal pulse oximetry surveilling the fetus under suspicion of hypoxia appears limited by the poor diagnostic power of the respiratory parameter saturation itself and by the impairment of the precision of the technology.