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.     

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.     

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 相似文献   

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.     

Decision-to-incision times and maternal and infant outcomes

OBJECTIVE: To measure decision-to-incision intervals and related maternal and neonatal outcomes in a cohort of women undergoing emergency cesarean deliveries at multiple university-based hospitals comprising the National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network. METHODS: All women undergoing a primary cesarean delivery at a Network center during a 2-year time span were prospectively ascertained. Emergency procedures were defined as those performed for umbilical cord prolapse, placental abruption, placenta previa with hemorrhage, nonreassuring fetal heart rate pattern, or uterine rupture. Detailed information regarding maternal and neonatal outcomes, including the interval from the decision time to perform cesarean delivery to the actual skin incision, was collected. RESULTS: Of the 11,481 primary cesarean deliveries, 2,808 were performed for an emergency indication. Of these, 1,814 (65%) began within 30 minutes of the decision to operate. Maternal complication rates, including endometritis, wound infection, and operative injury, were not related to the decision-to-incision interval. Measures of newborn compromise including umbilical artery pH less than 7 and intubation in the delivery room were significantly greater when the cesarean delivery was commenced within 30 minutes, likely attesting to the need for expedited delivery. Of the infants with indications for an emergency cesarean delivery who were delivered more than 30 minutes after the decision to operate, 95% did not experience a measure of newborn compromise. CONCLUSION: Approximately one third of primary cesarean deliveries performed for emergency indications are commenced more than 30 minutes after the decision to operate, and the majority were for nonreassuring heart rate tracings. In these cases, adverse neonatal outcomes were not increased. LEVEL OF EVIDENCE: II-2.     

Cesarean delivery for nonreassuring fetal heart rate tracing

An understanding of cesarean delivery for nonreassuring fetal heart rate tracing is important for several reasons. This article describes the prevalence of cesarean for nonreassuring fetal heart rate tracing and risk factors, indicates what type of fetal heart rate tracing abnormalities prompts cesarean delivery, reiterates the intrauterine resuscitation that the American College of Obstetricians and Gynecologists guidelines, and suggests steps clinicians should undertake to minimize legal liability.     

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.     

Umbilical arterial pH < 7.00 in newborns delivered by nonelective cesarean delivery: risk factors and peripartum outcomes

The objective of this study was to compare the risk factors and peripartum outcomes among patients who had nonelective cesarean delivery with umbilical arterial pH < versus > or = 7.00. A case-control study of parturients who delivered by nonelective cesarean delivery and had a neonate with a pH < 7.00 were compared with the next four patients who delivered abdominally but had a newborn with a normal pH. Among 45 newborns with pH < 7.00 the rate of cesarean delivery for nonreassuring fetal heart rate was significantly more common in the case (56%) than control group (16%). The rates of end organ failure and neonatal death were similar for both groups. Although newborns with pH < 7.00 were significantly more likely to have cesarean delivery for nonreassuring fetal heart rate patterns and be admitted to the neonatal intensive care unit, there was no means to identify these patients until the abnormalities in tracing developed.     

Intrapartum fetal heart rate monitoring

Intrapartum fetal heart rate monitoring is commonly used to evaluate fetal status in labor, despite a lack of convincing randomized studies to support its use. The National Institutes of Health have helped standardize fetal heart rate monitoring terminology with their 1997 task force report, which will aid clinicians and scientists in their goal of providing quality care and research. The American College of Obstetricians and Gynecologists has recommended the term nonreassuring fetal status for electronic fetal monitor patterns that are not normal; however, Vanderbilt continues to use the terms fetal stress and fetal distress, using specific criteria for each. The approximately 30% of fetal heart rate tracings labeled as fetal stress (or nonreassuring fetal status) can be evaluated further by the use of fetal pulse oximetry, a new technology currently under evaluation in this country.     

Continuous intrapartum pH, pO2, pCO2, and SpO2 monitoring

The goal of intrapartum surveillance and its further development is better patient care for both the fetus and the gravida. A normal FHR pattern is usually associated with the delivery of a normal well-oxygenated infant; however, a nonreassuring FHR is not always associated with the delivery of a compromised infant. This situation has led to an increase in unnecessary obstetric interventions in the form of a rising cesarean section rate. Fetal scalp sampling was developed in an attempt to improve the predictive value of electronic FHR monitoring, but because this technique is not widely used, management decisions are frequently made using FHR patterns alone. Much research has been performed in the search for a continuous biochemical measurement of fetal status, including continuous pH, pO2, or pCO2 and various combinations of these methodologies. None of these measurements are used in current clinical practice, mainly owing to technical problems and difficulties associated with the continuous direct measurement of these parameters in fetal blood throughout labor. The promising new field of fetal pulse oximetry has the potential to provide reliable, meaningful, and reproducible data as shown in early cross-sectional studies and more recent longitudinal studies. By identifying developing hypoxia, this technology may reduce the uncertainty associated with electronic FHR monitoring. Fetal pulse oximetry may also provide critical information relating to the detection and management of the hypoxic fetus. Any new method of intrapartum fetal monitoring requires careful evaluation to assess its potential value before its introduction into clinical practice. The use of fetal SpO2 monitoring in the presence of a nonreassuring FHR pattern is being examined in a multicenter randomized controlled trial. This study will address the question of whether supplementary monitoring of fetal SpO2 levels can lead to a reduction in the cesarean section rate for fetal distress. The available data on fetal noninvasive pulse oximetry have been obtained from a combination of well-designed cohort studies (level II-2 evidence) or from earlier multiple time series (level II-3 evidence). The results from the US Multicenter Trial (level I evidence) should provide a significant addition to current evidence. A continuous fetal noninvasive monitor measuring fetal oxygenation directly could lead to an improvement in the sensitivity and specificity of fetal surveillance. This improvement could ultimately result in a reduction in unnecessary interventions by differentiating hypoxic fetuses from nonhypoxic fetuses and, more importantly, may lead to earlier intervention for fetuses in danger of serious compromise.     

Emergency cesarean delivery for nonreassuring fetal heart rate tracings. Compliance with ACOG guidelines

OBJECTIVE: To review the English-language literature from 1990 to 2000 on cesarean delivery for "fetal distress" and assess compliance with American College of Obstetricians and Gynecologists (ACOG) guidelines. STUDY DESIGN: A PubMed search with the search items cesarean, fetal distress, cesarean, nonreassuring fetal heart rate, cesarean, neonatal acidosis and cesarean, umbilical arterial pH was undertaken. Excluded from the search were case reports, letters to the editor, focus on fetal anomaly, combinations with other reasons for operative delivery (either abdominally or vaginally) or absence of pertinent information. RESULTS: Among 392 articles from the search, 169 met the inclusion criteria. Three reports provided detailed information on use of scalp pH; use occurred in 5% (60/1,128) of emergency cesareans. Three reports provided data on the use of tocolytics for intrauterine resuscitation; the combined result was 16% (201/1,261). Five reports assessed the decision-to-incision interval within 30 minutes; in 59% (262/446) of cases it was achieved. Five reports contained cord pH information on 340 emergency cesarean deliveries; umbilical arterial pH was < 7.00 in 10%. CONCLUSION: Physician use of, and compliance with, ACOG guidelines for emergency cesarean deliveries is difficult to assess, and incomplete compliance appears commonplace.     

Impact of abnormal results of outpatient fetal heart rate monitoring on maternal intervention in labor

OBJECTIVE: To conduct a retrospective, cohort study to determine the impact of abnormal outpatient fetal heart rate (FHR) testing on maternal interventions in labor, including labor induction, operative vaginal delivery and unplanned cesarean section. STUDY DESIGN: Our cohort consisted of 1,386 women with singleton gestations who had outpatient fetal nonstress testing within 1 week prior to giving birth etween 1993 and 1998. Antepartum FHR records were interpreted as reassuring or nonreassuring, and pregnancy records were abstracted for background medical information, labor interventions and pregnancy outcomes. Logistic regression models were used to describe the association between abnormal outpatient monitoring results and maternal interventions in labor. RESULTS: After adjusting for potential confounders (maternal age, race, prior history of cesarean section, antepartum indications for monitoring, fetal presentation and abnormal fetal heart rate patterns in labor), women with nonreassuring monitoring were 90% more likely to undergo induction. The 2 groups were similar in operative vaginal delivery rates, but pregnancies with nonreassuring testing were more than twice as likely to end with an unplanned cesarean section. CONCLUSION: Abnormal outpatient antenatal FHR testing may be independently associated with an increased risk of unplanned cesarean section.     

Update on intrapartum fetal pulse oximetry

This article examines the current status of fetal pulse oximetry (FPO) as a means of intrapartum assessment of fetal wellbeing. FPO has been developed to a stage where it is a safe and accurate indicator of intrapartum fetal oxygenation. In general, sliding the FPO sensor along the examiner's fingers and through the cervix, to lie alongside the fetal cheek or temple is easy The recent publication of a randomised controlled trial (RCT) of FPO versus conventional intrapartum monitoring has validated its use to reduce caesarean section rates for nonreassuring fetal status. An Australian multicentre RCT is currently underway. Maternal satisfaction rates with FPO are high. FPO may be used during labour when the electronic fetal heart rate trace is nonreassuring or when conventional monitoring is unreliable, such as with fetal arrhythmias. If the fetal oxygen saturation (FSpO2) values are < 30%, prompt obstetric intervention is indicated, such as fetal scalp blood sampling or delivery FSpO2 monitoring should not form the sole basis of intrapartum fetal welfare assessment. Rather, the whole clinical picture should be considered.     

Effectiveness of pulse oximetry versus fetal electrocardiography for the intrapartum evaluation of nonreassuring fetal heart rate

Objectives

To compare the effectiveness of pulse oximetry and fetal electrocardiography in the management of labor with nonreassuring fetal heart rate (NRFHR).

Study design

This randomized experimental study consisted of two arms. In group 1 we used pulse oximetry and in group 2 we used STAN^® technology. The participants in each group were 90 pregnant women with a full-term singleton fetus in cephalic presentation and cardiotocographic tracings compatible with NRFHR. We compared the following variables: rate of cesarean delivery, indications for operative delivery due to NRFHR, and repercussions on the newborn's acid–base status.

Results

The two groups differed significantly in the mode of delivery, with a cesarean delivery rate of 47.6% in group 1 vs. 30% in group 2 (p = 0.032). The groups did not differ in the indications for ending labor due to NRFHR (62% vs. 61%, NS). In terms of neonatal outcomes, the 1-min Apgar score was 6 or lower in 17.8% of the group 1 neonates vs. 4.44% of the group 2 neonates (p < 0.001). The groups also differed significantly in umbilical cord vein pH (7.23 vs. 7.27) and pCO₂ (57.27 vs. 46.86) at birth.

Conclusions

Fetal electrocardiography with the STAN^® 21 system was more effective in detecting good fetal status and thus in identifying cases in which labor could proceed safely. Intrapartum surveillance with the STAN^® 21 system reduced the rate of emergency cesarean delivery.     

Cord gas analysis, decision-to-delivery interval, and the 30-minute rule for emergency cesareans.

OBJECTIVE: Our primary objective was to examine the relationship between umbilical arterial gas analysis and decision-to-delivery interval for emergency cesareans performed for nonreassuring fetal status to determine if this would validate the 30-minute rule. STUDY DESIGN: For this retrospective cohort study, all cesarean deliveries performed for nonreassuring fetal status from September 2001 to January 2003 were reviewed. A synopsis of clinical information that would have been available to the clinician at the time of delivery and the last hour of the electronic fetal heart rate tracing prior to delivery were reviewed by three different maternal-fetal medicine specialists masked to outcome, who classified each delivery as either emergent (delivery as soon as possible) or urgent (willing to wait up to 30 minutes for delivery) since immediacy of the fetal condition is the key factor affecting the type of anesthesia used. RESULTS: Of 145 cesareans performed for nonreassuring fetal status during this period, 117 patients met criteria for entry, of which 34 were classified as emergent and 83 as urgent. Kappa correlation was 0.35, showing only fair/moderate agreement between reviewers. In the emergent group, general anesthesia was more common (35.3%, 10.8%, p=0.003), and the decision-to-delivery interval was 14 minutes shorter (23.0+/-15.3, 36.7+/-14.9 minutes, p<0.001). Linear regression showed a statistically significant relationship between increasing decision-to-delivery interval and umbilical arterial pH (r=0.22, p=0.02) and base excess (r=0.33, p<0.001) showing that delivery proceeded sooner for most of those with the worst cord gases, with a gradual improvement over time. For the 13 (11%) neonates with cord gases placing them at increased risk for long-term neurologic sequelae, the decision-to-delivery interval was 24.7+/-14.6 minutes (range 6 to 50 minutes), and 3/13 (23%) were classified as urgent rather than emergent. CONCLUSION: Electronic fetal monitoring shows considerable variation in interpretation among maternal-fetal medicine specialists and is not a sensitive predictor of the fetus developing metabolic acidosis. There is no deterioration in cord gas results after 30 minutes, and most neonates delivered emergently or urgently for nonreassuring fetal status even when born after 30 minutes have normal cord gases. The 30-minute rule is a compromise that reflects the time it takes the fetus to develop severe metabolic acidosis, our imprecision in its identification, and its rarity in the presence of nonreassuring fetal monitoring.     

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 ≥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.     

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.     

Acute fetal distress

Three different clinical patterns of acute fetal distress may be observed during labor: an ante-partum hypoxia with a persistent nonreactive and "fixed" fetal heart rate (FHR) on admission to the hospital, a progressive intra-partum asphyxia manifested, as the labor continues, by a substantial rise in baseline heart rate, a loss of variability and repetitive severe variable or late decelerations, and finally, as a result of a catastrophic event, a sudden prolonged FHR deceleration to approximately 60 beats per minute lasting until delivery. However the majority of fetuses with nonreassuring tracings of FHR are neurologically intact, as evidenced by the high false-positive rate of electronic fetal monitoring (EFM). Therefore the diagnosis of fetal distress must be corroborated by complementary methods, such as continuous recording of the fetal electrocardiogram or computed-assisted EFM, fetal pulse oximetry or fetal scalp sampling with immediate determination of blood gases or lactates. Defavorable outcome of an acute fetal distress leading to neonatal encephalopathy or death is best predicted by a persisting low Apgar score (<3) for more than 5 minutes and by a severe metabolic acidosis (umbilical artery pH<7,00 and base-excess>-12mmol/l).     

Fetal pulse oximetry: an adjunct to electronic fetal heart rate monitoring

Electronic fetal heart rate monitoring is routinely used as an indirect measure of fetal oxygenation, yet its value continues to be questioned. With a nonreassuring fetal heart rate pattern, the clinician often needs additional information about fetal oxygen status. Fetal pulse oximetry is a new fetal assessment technology. After consideration of the results of a multicenter randomized, controlled, clinical trial on fetal pulse oximetry in the United States, the U.S. Food and Drug Administration approved the technology for clinical use on May 12, 2000. The results of this trial are anticipated to be published in late 2000.     

Fetal pulse oximetry: duration of desaturation and intrapartum outcome.

OBJECTIVE: To analyze labor outcomes in relation to masked fetal arterial oxyhemoglobin saturation values above or below 30%. METHODS: Consenting gravidas with uncomplicated pregnancies at or beyond 36 weeks' gestation underwent continuous fetal pulse oximetry. Pregnancy outcomes were compared between two groups: women with fetuses with at least one epoch of arterial oxyhemoglobin saturation below 30% (10 seconds or longer) and women with fetuses without such an episode. We also attempted to ascertain whether duration of saturation below 30% correlated with fetal compromise. RESULTS: We measured arterial oxyhemoglobin saturation in 129 fetuses, 69 (53%) of whom had at least one epoch of saturation below 30%. There were no statistically significant differences in labor and delivery outcomes between the high-saturation and low-saturation groups (eg, cesarean delivery: 13 versus 9%, P = .41; umbilical artery [UA] pH less than 7.20: 10 versus 9%, P > .999). However, as duration of fetal arterial oxyhemoglobin saturation below 30% increased from 10 seconds to longer than 9 consecutive minutes, the incidence of fetal compromise (considered present when at least one of the following criteria was met: cesarean delivery for nonreassuring fetal heart rate pattern, UA pH less than 7.20, admission to the special care nursery, or 5-minute Apgar score not more than 3) increased significantly (P = .002). The threshold duration of fetal arterial oxyhemoglobin saturation below 30% associated with increased fetal compromise was 2 minutes. CONCLUSION: Transient fetal arterial oxyhemoglobin saturation values below 30% are common during normal labor and did not predict fetal compromise. Fetal arterial oxyhemoglobin saturation values less than 30% for 2 minutes or longer might be associated with fetal compromise.