Maternal perceptions of labor with fetal monitoring by pulse oximetry in a research setting

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.

Fetal pulse oximetry for fetal assessment in labour

BACKGROUND

The use of conventional cardiotocographic (CTG) monitoring of fetal well-being during labour is associated with an increased caesarean section rate, compared with intermittent auscultation of the fetal heart rate, resulting in a reduction in neonatal seizures, although no differences in other neonatal outcomes. To improve the sensitivity of this test and therefore reduce the number of caesarean sections performed for nonreassuring fetal status, several additional measures of evaluating fetal well-being have been considered. These have demonstrated some effect on reducing caesarean section rates, for example, fetal scalp blood sampling for pH estimation/lactate measurement. The adaptation of pulse oximetry for use in the unborn fetus could potentially contribute to improved evaluation during labour and therefore lead to a reduction in caesarean sections for nonreassuring fetal status, without any change in neonatal outcomes.

OBJECTIVES

To compare the effectiveness and safety of fetal intrapartum pulse oximetry with other surveillance techniques.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 May 2014), contacted experts in the field and searched reference lists of retrieved studies. In previous versions of this review, we performed additional searches of MEDLINE, Embase and Current Contents. These searches were discontinued for this review update, as they consistently failed to identify any trials that were not shown in the Cochrane Pregnancy and Childbirth Group's Trials Register.

SELECTION CRITERIA

All published and unpublished randomised controlled trials that compared maternal and fetal outcomes when fetal pulse oximetry was used in labour, (i) with or without concurrent use of conventional fetal surveillance, that is, cardiotocography (CTG), compared with using CTG alone or (ii) with or without concurrent use of both CTG and other method(s) of fetal surveillance, such as fetal electrocardiography (ECG) plus CTG.

DATA COLLECTION AND ANALYSIS

At least two independent review authors performed data extraction. We sought additional information from the investigators of three of the reported trials.

MAIN RESULTS

We included seven published trials: six comparing fetal pulse oximetry and CTG with CTG alone (or when fetal pulse oximetry values were blinded) and one comparing fetal pulse oximetry plus CTG with fetal ECG plus CTG. The published trials, with some unpublished data, were at high risk of bias in terms of the impractical nature of blinding participants and clinicians, as well as high risk or unclear risk of bias for outcome assessor for all but one report. Selection bias, attrition bias, reporting bias and other sources of bias were of low or unclear risk. The trials reported on a total of 8013 pregnancies. Differing entry criteria necessitated separate analyses, rather than meta-analysis of all trials.Systematic review of four trials from 34 weeks not requiring fetal blood sampling (FBS) prior to study entry showed no evidence of differences in the overall caesarean section rate between those monitored with fetal oximetry and those not monitored with fetal pulse oximetry or for whom the fetal pulse oximetry results were masked (average risk ratio (RR) 0.99 using random-effects, 95% confidence intervals (CI) 0.86 to 1.13, n = 4008, I² = 45%). There was evidence of a higher risk of caesarean section in the group with fetal oximetry plus CTG than in the group with fetal ECG plus CTG (one study, n = 180, RR 1.56, 95% CI 1.06 to 2.29). Neonatal seizures and neonatal encephalopathy were rare in both groups. No studies reported details of long-term disability.There was evidence of a decrease in caesarean section for nonreassuring fetal status in the fetal pulse oximetry plus CTG group compared to the CTG group, gestation from 34 weeks (average RR (random-effects) 0.65, 95% CI 0.46 to 0.90, n = 4008, I² = 63%). There was no evidence of differences between groups in caesarean section for dystocia, although the overall incidence rates varied between the trials.

AUTHORS' CONCLUSIONS

The addition of fetal pulse oximetry does not reduce overall caesarean section rates. One study found a higher caesarean section rate in the group monitored with fetal pulse oximetry plus CTG, compared with fetal ECG plus CTG. The data provide limited support for the use of fetal pulse oximetry when used in the presence of a nonreassuring CTG, to reduce caesarean section for nonreassuring fetal status. A better method than pulse oximetry is required to enhance the overall evaluation of fetal well-being in labour.

Intrapartum oximetry of the fetus

Fetal monitoring during labor aims to identify fetal problems which, if uncorrected, may result in morbidity or death. A nonreassuring or abnormal fetal heart rate trace by cardiotocography (CTG) does not necessarily equate with fetal hypoxia and/or acidosis. However, in the absence of more objective data, the use of CTG often results in variable, but inappropriately high, operative delivery rates (forceps, vacuum, or cesarean delivery) for nonreassuring fetal status in many hospitals. The addition of fetal pulse oximetry (FPO) has the potential to improve the assessment of fetal well-being during labor. In this review we consider several aspects of FPO. Several factors, such as sensor to skin contact, uterine contractions, fetal hair, and caput succedaneum, influence the performance and use of FPO. Issues such as clinicians' perspectives of FPO sensor placement, maternal perspectives of FPO during labor, and an economic analysis have all favored FPO. Several randomized controlled trials (RCTs) of FPO reported a reduction in cesarean delivery for nonreassuring fetal status when FPO was added to conventional CTG monitoring, with no difference in overall cesarean delivery rates. One large RCT reported no difference in mode of birth for any indication. Several issues relevant to the future of FPO have been addressed by these RCTs, the major issue being that it makes no difference to cesarean rates. It may be argued that FPO has a valid clinical use in monitoring the fetus with congenital heart block. Additionally, in situations of nonreassuring fetal status and dystocia, FPO may provide the necessary reassurance until adequate resources for cesarean delivery are available.

Fetal pulse oximetry for fetal assessment in labour

BACKGROUND

Pulse oximetry could contribute to the evaluation of fetal well-being during labour.

OBJECTIVES

To compare the effectiveness and safety of fetal pulse oximetry with conventional surveillance techniques.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (November 2006), MEDLINE (1994 to November 2006), EMBASE (1994 to November 2006) and Current Contents (1994 to November 2006).

SELECTION CRITERIA

All published and unpublished randomised controlled trials that compared maternal and fetal outcomes when fetal pulse oximetry was used in labour, with or without concurrent use of conventional fetal surveillance, compared with using cardiotocography (CTG) alone.

DATA COLLECTION AND ANALYSIS

At least two independent authors performed data extraction. Analyses were performed on an intention-to-treat basis. We sought additional information from the investigators of three of the reported trials.

MAIN RESULTS

Five published trials comparing fetal pulse oximetry and CTG with CTG alone (or when fetal pulse oximetry values were blinded) were included. The published trials, with some unpublished data, reported on a total of 7424 pregnancies. Differing entry criteria necessitated separate analyses, rather than meta-analysis of all trials. Four trials reported no significant differences in the overall caesarean section rate between those monitored with fetal oximetry and those not monitored with fetal pulse oximetry or for whom the fetal pulse oximetry results were masked. Neonatal seizures and hypoxic ischemic encephalopathy were rare. No studies reported details of assessment of long-term disability. There was a statistically significant decrease in caesarean section for nonreassuring fetal status in the fetal pulse oximetry plus CTG group compared to the CTG group in two analyses: (i) gestation from 36 weeks with fetal blood sample (fetal blood sampling) not required prior to study entry (relative risk (RR) 0.68, 95% confidence interval (CI) 0.47 to 0.99); and (ii) when fetal blood sampling was required prior to study entry (RR 0.03, 95% CI 0.00 to 0.44). There was no statistically significant difference in caesarean section for dystocia when fetal pulse oximetry (fetal pulse oximetry) was added to CTG monitoring, compared with CTG monitoring alone, although the incidence rates varied between the trials.

AUTHORS' CONCLUSIONS

The data provide limited support for the use of fetal pulse oximetry when used in the presence of a nonreassuring CTG, to reduce caesarean section for nonreassuring fetal status. The addition of fetal pulse oximetry does not reduce overall caesarean section rates. A better method to evaluate fetal well-being in labour is required.

Intrapartum fetal monitoring today

The literature on intrapartum fetal monitoring is reviewed emphasizing the pathophysiology, and current practice guidelines are discussed. FHR monitoring, ancillary tests, and investigational modalities are considered.

Fetal pulse oximetry for fetal assessment in labour

BACKGROUND

Fetal pulse oximetry (FPO) may contribute to the evaluation of fetal well-being during labour.

OBJECTIVES

To compare the effectiveness and safety of FPO with conventional surveillance techniques, using the results of randomised controlled trials.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group trials register (31 July 2004) and conducted a systematic literature search of MEDLINE (1994 to July 2004), EMBASE (1994 to July 2004) and Current Contents (1994 to July 2004).

SELECTION CRITERIA

All published and unpublished randomised controlled trials (RCTs) that compared maternal and fetal/neonatal/infant outcomes when FPO was used in labour, with or without concurrent use of conventional fetal surveillance, compared with using cardiotocography (CTG) alone.

DATA COLLECTION AND ANALYSIS

Two independent reviewers performed data extraction. Analyses were performed on an intention-to-treat basis. We sought additional information from the investigators of the one reported trial.

MAIN RESULTS

One published RCT (comparing FPO and CTG with CTG alone) was included; and two ongoing RCTs were identified. The single included RCT reported on 1010 cases. Unpublished pilot data were available for some outcomes to give a total of 1190 cases. There was no difference in the overall caesarean section rate between the two groups (relative risk (RR) 1.12, 95% confidence interval (CI) 0.91 to 1.37). There were less caesarean sections for nonreassuring fetal status in the FPO plus CTG group compared with the CTG only group (RR 0.45, 95% CI 0.28 to 0.72). The only reported neonatal seizure occurred in the CTG only group (RR 0.29 95% CI 0.01 to 7.08). Use of FPO with CTG decreased operative delivery (caesarean section, forceps, vacuum) for nonreassuring fetal status (RR 0.71, 95% CI 0.55 to 0.93) compared with CTG alone. No differences were seen for overall operative deliveries, endometritis, intrapartum or postpartum haemorrhage, uterine rupture, low Apgar scores, umbilical arterial pH or base excess, admission to the neonatal intensive care unit or fetal/neonatal death.

REVIEWERS' CONCLUSIONS

The one published RCT reported that FPO decreased the caesarean section rate and operative delivery rates for nonreassuring fetal status, without adversely affecting maternal or fetal/neonatal outcomes. However, no difference was seen in the overall caesarean section (CS) or operative delivery rates because more CS were performed for dystocia in the FPO group. Further RCTs may address dystocia in labours monitored with FPO, maternal satisfaction with fetal monitoring and labour, long-term neurodevelopmental outcome of infants who exhibited nonreassuring fetal status in labour and costs of FPO.

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.

Intrapartum fetal pulse oximetry. Part 2: Clinical application

Part II continues by discussing the clinical application of fetal pulse oximetry in intrapartum fetal surveillance as reviewed in the literature. It profiles the predictive ability of fetal pulse oximetry and its correlation with conventional methods of fetal monitoring. In addition, an account is made of its limitations, safety, and acceptability in clinical practice.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians

LEARNING OBJECTIVES

After completion of this article, the reader will be able to describe the predictive abilities of fetal pulse oximetry and its correlation with conventional methods of fetal monitoring, to define the critical threshold of fetal oxygen saturation, and to summarize the safety of fetal pulse oximetry.