How long does a fetal scalp blood sample take?

Fetal scalp stimulation for assessing fetal well-being during labour

BACKGROUND

Continuous fetal heart rate monitoring by cardiotocography (CTG) is used in labour for women with complicated pregnancies. Fetal heart rate abnormalities are common and may result in the decision to expedite delivery by caesarean section. Fetal scalp stimulation (FSS) is a second-line test of fetal well-being that may provide reassurance that the labour can continue.

OBJECTIVES

To evaluate methods of FSS as second-line tests of intrapartum fetal well-being in cases of non-reassuring CTG. FSS and CTG were compared to CTG alone, and to CTG with fetal blood sampling (FBS).

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register (which includes trials from CENTRAL, MEDLINE, Embase, CINAHL, the WHO ICTRP and conference proceedings), ClinicalTrials.gov (18 October 2022), and reference lists of retrieved studies.

SELECTION CRITERIA

Eligible studies were randomised controlled trials (RCTs) that compared any form of FSS to assess fetal well-being in labour. Quasi-RCTs, cluster-RCTs and studies published in abstract form were also eligible for inclusion, but none were identified.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for inclusion and risk of bias, extracted data and checked them for accuracy. We assessed the certainty of the evidence using the GRADE approach.

MAIN RESULTS

Two trials, involving 377 women, met the inclusion criteria for this review. Both trials were conducted in hospital settings and included women with singleton, term (37+0 weeks or more) pregnancies, a cephalic presentation, and abnormal CTG. Follow-up was until hospital discharge after the birth. A pilot trial of 50 women in a high-income country (Ireland) compared CTG and digital fetal scalp stimulation (dFSS) with CTG and fetal blood sampling (FBS). A single-centre trial of 327 women in a lower middle-income country (India) compared CTG and manual fetal stimulation (abdominal or vaginal scalp stimulation) with CTG alone. The two included studies were at moderate or unclear risk of bias. Both trials provided clear information on allocation concealment but it was not possible to blind participants or health professionals in relation to the intervention. Although objective outcome measures were reported, outcome assessment was not blinded or blinding was unclear. dFSS and CTG versus FBS and CTG There were no perinatal deaths and data were not reported for neurodevelopmental disability at >/= 12 months. The risk of caesarean section (CS) may be lower with dFSS compared to FBS (risk ratio (RR) 0.38, 95% confidence interval (CI) 0.16 to 0.92; 1 pilot trial, 50 women; very low-certainty evidence) but the evidence is very uncertain. There were no cases of neonatal encephalopathy reported. The evidence was also very uncertain between dFSS and FBS for assisted vaginal birth (RR 1.44, 95% CI 0.76 to 2.75; very low-certainty evidence) and for the spontaneous vaginal birth rate (RR 2.33, 95% CI 0.68 to 8.01, very low-certainty evidence). Maternal acceptability of the procedures was not reported. FSS and CTG versus CTG alone Manual stimulation of the fetus was performed either abdominally (92/164) or vaginally (72/164). There were no perinatal deaths and data were not reported for neurodevelopmental disability at >/= 12 months. There may be little differences in the risk of CS on comparing manual fetal stimulation and CTG with CTG alone (RR 0.83, 95% CI 0.59 to 1.18; 1 trial, 327 women; very low-certainty evidence), but again the evidence was very uncertain. There were no cases of neonatal encephalopathy reported. There may be no differences in the risk of assisted vaginal birth (RR 1.43, 95% CI 0.78 to 2.60; very low-certainty evidence) or in the rates of spontaneous vaginal birth (RR 1.01, 95% CI 0.85 to 1.21, very low-certainty evidence), but again the evidence is very uncertain. Maternal acceptability of abdominal stimulation/FSS was not reported although 13 women withdrew consent after randomisation due to concerns about fetal well-being.

AUTHORS' CONCLUSIONS

There is very low-certainty evidence available which makes it unclear whether stimulating the fetal scalp is a safe and effective way to confirm fetal well-being in labour. Evidence was downgraded based on limitations in study design and imprecision. Further high-quality studies of adequate sample size are required to evaluate this research question. In order to be generalisable, these trials should be conducted in different settings, including broad clinical criteria at both preterm and term gestational ages, and standardising the method of stimulation. There is an ongoing study (FIRSST) that will be incorporated into this review in a subsequent update.

Digital fetal scalp stimulation (dFSS) versus fetal blood sampling (FBS) to assess fetal wellbeing in labour-a multi-centre randomised controlled trial: Fetal Intrapartum Randomised Scalp Stimulation Trial (FIRSST NCT05306756)

BACKGROUND

Cardiotocography (CTG) is a screening test used to detect fetal hypoxia in labour. It has a high false positive rate resulting in many potentially unnecessary caesarean sections. Fetal blood sampling (FBS) is a second-line test of the acid-base status of the fetus. It is used to provide either reassurance that it is safe for labour to continue or objective evidence of compromise so that delivery can be expedited. Digital fetal scalp stimulation (dFSS) to elicit a fetal heart rate acceleration is an alternative less invasive second-line test of fetal wellbeing. This study aims to provide robust evidence on the role of these two second-line tests in assessing fetal wellbeing and potentially preventing operative delivery.

METHODS

A multi-centre parallel group randomised controlled trial (RCT) is planned in four maternity centres in Ireland. The study aims to recruit 2500 nulliparous women with a term (≥37+0 weeks) singleton pregnancy who require a second-line test of fetal wellbeing in labour due to an abnormal CTG. Women will be allocated randomly to dFSS or FBS on a 1:1 ratio. The primary outcome is caesarean section. With 1250 women in each arm, the study will have 90% power to detect a difference of 5-6%, at a two-sided alpha significance level of 5%, assuming a caesarean section rate of at least 20% in the dFSS group.

DISCUSSION

If the proposed study shows evidence that dFSS is a safe, reliable and effective alternative to FBS, this would have ground-breaking implications for labour management worldwide. It could potentially lead to a reduction in invasive procedures and emergency caesarean sections.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05306756. Registered on 31 March 2022. The trial commenced enrolment on 10 May 2022. Ethical committee approval has been granted by the Research Ethics Committee (REC) of each hospital: Dublin/CWIUH REC: 12.06.2019; Cork/UCC REC: 29.11.2019; Galway/NUIG REC: 06.09.2019; Limerick/UL REC: 30.09.2019.

How to reduce fetal scalp blood sampling? A retrospective study evaluating the diagnostic value of scalp stimulation to predict fetal wellbeing assessed by scalp blood sampling

BACKGROUND

The Fetal Blood Sample (FBS) is used as an indicator of fetal acidosis during labor. Its place is discussed through the lack of randomized trials, as well as the limitations related to the technical procedure. An alternative could be the Fetal Scalp Stimulation (FSS).

AIM

Our objective was to describe the FSS diagnostic value to predict fetal wellbeing defined from FBS.

METHODS

The FSS consisted in a digital scalp stimulation for 15 s. Test was negative when an acceleration and/or a normal variability were elicited in the 2 min following. FSS was performed before each FBS which was classified as normal when pH was > 7.25. The diagnostic value was assessed by sensibility, specificity, positive and negative predictive values.

FINDINGS

148 women were included in our center from February to December 2019. Of the 191 FBS procedures, when accelerations were elicited sensibility was 58,3 (36.8-77.1), specificity was 67,5 (59.3-75), positive predictive value was 20,9 (12.5-32.9) and negative predictive value was 91.7 % (95 %CI, 85-95.5).

DISCUSSION

FBS is considered as the gold standard in our study which could be discussed as it is abandoned in some countries because of its questioned reliability and the lack of controlled randomized trials.

CONCLUSION

This study suggests that FSS could be an interesting alternative adjunctive test to perform in the first instance as it seems to be reliable, non-invasive and easy to perform in order to limit FBS only to absence of acceleration after FSS.

Comparing second-line tests to assess fetal wellbeing in Labor: a feasibility study and pilot randomized controlled trial

Objective: To explore the feasibility of conducting a randomized controlled trial (RCT) designed to compare the performance of digital fetal scalp stimulation (dFSS) and fetal blood sampling (FBS) as second-line tests of fetal wellbeing in Labor.Design: A feasibility study included 66 women who consented to both dFSS and FBS performed contemporaneously. A pilot randomized controlled trial included 50 women who were randomized to either dFSS or FBS.Setting: University-affiliated maternity hospital.Population: Women in Labor who required second-line testing of fetal well-being following abnormal fetal heart rate monitoring.Outcome measures: The primary outcome of interest was delivery by emergency cesarean section. Secondary outcomes included maternal and perinatal morbidity outcomes and procedural factors.Results: Of the 66 women recruited to the feasibility study 50 (76%) received the two interventions as per protocol. The demographic data indicated that future RCT should be limited to nulliparous women. After initial training and reminders, the dFSS procedure appeared to be acceptable to patients and clinicians and was interpreted appropriately. Recruitment of eligible women to the pilot RCT was successful (88%) with 50 of 63 eligible women randomized (79%) and no drop-outs. The cesarean section rate was high in both arms as expected with a cohort of women requiring second-line tests for abnormal fetal heart rate monitoring in Labor (5/25; 20% dFSS versus 13/25; 52% FBS, p = .018). Conservative estimates suggest that a sample size of 2500 randomized women would be required for a definitive RCT.Conclusions: This study suggests that dFSS, which has the potential to be a reliable alternative to FBS, could be evaluated in a well-designed randomized controlled trial.Trial registration: The definitive trial has been registered ISRCTN 13295826.

Sensors for Fetal Hypoxia and Metabolic Acidosis: A Review

This article reviews existing clinical practices and sensor research undertaken to monitor fetal well-being during labour. Current clinical practices that include fetal heart rate monitoring and fetal scalp blood sampling are shown to be either inadequate or time-consuming. Monitoring of lactate in blood is identified as a potential alternative for intrapartum fetal monitoring due to its ability to distinguish between different types of acidosis. A literature review from a medical and technical perspective is presented to identify the current advancements in the field of lactate sensors for this application. It is concluded that a less invasive and a more continuous monitoring device is required to fulfill the clinical needs of intrapartum fetal monitoring. Potential specifications for such a system are also presented in this paper.

Infant outcome at four years of age after intrapartum sampling of scalp blood lactate for fetal assessment. A cohort study

OBJECTIVE

To correlate the value of lactate in fetal scalp blood at delivery and the outcomes of the offspring at four years of age.

METHODS

Cases where scalp blood lactate was taken within sixty minutes before delivery were identified from the randomized trial "Determination of pH or lactate in fetal scalp blood in management of intrapartum fetal distress". Data were grouped according to the generally accepted cutoffs for normality, pre-acidemia, acidemia and concentrations above mean +2 SD during the second stage. The outcome measures included gross-/fine motor function, vision, hearing, speaking and cognitive disorders, signs of central motor damage and referral to specialized pediatric services.

RESULTS

307 cases were available for final analyse. With normal scalp lactate concentration, the number of children with a diagnosed disorder was lower compared to the pre-acidemic/acidemic groups, although the findings were only significant for fine motor dysfunction (p = 0.036). Elevated lactate values were significantly associated with increased risk for a poorer capacity of attention and understanding of instructions (OR 1.37, 95% CI 1.07-1.74), and for fine motor dysfunction (OR 1.22, 95% CI 1.00-1.49) at the age of four.

CONCLUSION

Higher levels of lactate in fetal scalp blood seems to be associated with increased risk of an aberrant developmental outcome at four years of age in some areas.

Reference values for Lactate Pro 2™ in fetal blood sampling during labor: a cross-sectional study

OBJECTIVE

Lactate Pro™ (LP1) is the only lactate meter evaluated for fetal scalp blood sampling (FBS) in intrapartum use. The reference values for this meter are: normal value <4.2 mmol/L, preacidemia 4.2-4.8 mmol/L, and acidemia >4.8 mmol/L. The production of this meter has been discontinued. An updated version, Lactate Pro 2TM (LP2), has been launched and is shown to be differently calibrated. The aims of the study were to retrieve a conversion equation to convert lactate values in FBS measured with LP2 to an estimated value if using LP1 and to define reference values for clinical management when using LP2.

STUDY DESIGN

A cross-sectional study was conducted at a university hospital in Sweden. A total of 113 laboring women with fetal heart rate abnormalities on cardiotocography (CTG) had FBS carried out. Lactate concentration was measured bedside with both LP1 and LP2 from the same blood sample capillary. A linear regression model was constructed to retrieve a conversion equation to convert LP2 values to LP1 values.

RESULTS

LP2 measured higher values than LP1 in all analyses. We found that 4.2 mmol/L with LP1 corresponded to 6.4 mmol/L with LP2. Likewise, 4.8 mmol/L with LP1 corresponded to 7.3 mmol/L with LP2. The correlation between the analyses was excellent (Spearman's rank correlation, r=0.97).

CONCLUSION

We recommend the following guidelines when interpreting lactate concentration in FBS with LP2: <6.4 mmol/L to be interpreted as normal, 6.4-7.3 mmol/L as preacidemia indicating a follow-up FBS within 20-30 min, and >7.3 mmol/L as acidemia indicating intervention.

Cervical dilatation and grade of doctor affects the interval between decision and result of fetal scalp blood sampling in labour

Fetal scalp blood sampling (FSBS) is used to provide information regarding fetal acid-base status during labour. This study assessed the interval between the decision to perform the procedure and obtaining the result and evaluated whether it is affected by cervical dilatation or the experience of the doctor. The median time for FSBS was 10 min. When cervical dilatation was ≤4 cm samples took approximately 30% longer to obtain. After adjustment for dilation, there were no significant differences between different grades of doctors. FSBS is shorter than previously reported; clinicians should be aware that procedures in early labour take longer to complete.

Experience of fetal scalp blood sampling during labor

Fetal scalp blood sampling (FBS) is often claimed to be painful for women in labor and difficult for obstetricians to perform. Our aim was to assess women's experience of pain during FBS and obstetricians' experience of difficulty in performing the test. At a tertiary center in Sweden, a questionnaire with answers on a 10-point scale was completed by 51 women and the obstetricians performing the test. Women's experience of pain had a median of 3.5. FBS was well tolerated in women who had epidural analgesia but might be associated with pain in women without. Higher maternal body mass index and less cervical dilation were associated with higher pain ratings. Obstetricians did not generally experience scalp sampling as difficult to perform (median score 3.0). However, the sampling procedure can be more complicated in situations with higher maternal body mass index, less cervical dilation, and a higher station of the fetal head.

Lactate study using umbilical cord blood: agreement between Lactate Pro hand-held devices with blood gas analyser and evaluation of lactate stability over time

BACKGROUND

Lactate measurements have become increasingly preferred over pH analysis in the evaluation of fetal acidaemia in labour. In a busy labour ward, often the umbilical cord may be sampled late and as a result yield unreliable lactate values.

AIM

To investigate the agreement of hand-held device Lactate Pro with a reference method blood gas analyser and evaluate the stability of umbilical cord lactate values over time.

METHODS

Prospective study carried out at elective caesarean section. Sixteen umbilical cords were double clamped immediately after delivery with paired arterial and venous blood samples collected by an independent researcher, at varying time intervals, and processed by two Lactate Pro devices and a reference method blood gas analyser.

RESULTS

A significant difference of -0.41 to 0.10 mmol/L was found when different groups of Lactate Pro devices were compared with blood gas analyser at lactate values up to 5.70 mmol/L, with average lactate value of 2.45 mmol/L. Over time, there is progressive rise in lactate samples obtained from the umbilical cord.

CONCLUSION

Lactate Pro devices have a significant difference, but when used in clinical practice on cord blood after delivery, this is unlikely to be meaningful. In intrapartum fetal surveillance, a systematic overestimation might lead to unnecessary intervention. It is possible to retrospectively predict the likely level of lactate at birth in delayed cord samples.

Intrapartum fetal asphyxia: study of umbilical cord blood lactate in relation to fetal heart rate patterns

PURPOSES

To correlate between umbilical artery cord blood lactate and acid-base status with intrapartum fetal heart rate monitoring, and to measure the reliability of umbilical cord blood lactate for prediction of early neonatal outcome.

METHODS

Sixty-six participants with intrapartum abnormal fetal heart rate monitoring and 60 participants with normal intrapartum recordings were recruited. The abnormal recordings included late onset, atypical variable and simple variable decelerations. After delivery, the arterial cord blood lactate, pH, actual base excess (ABE), and Apgar score were measured in all participants.

RESULTS

There was significant inverse correlation between cord lactate and pH and ABE in all participants (correlation coefficient = -0.7, p < 0.0001). The cord lactate was significantly higher in the late onset and atypical variable decelerations groups compared to control (p < 0.0001). There was no significant correlation between the Apgar score and blood lactate in all groups; however, the sensitivity and specificity of cord lactate to predict low score at 5 min were higher in comparison to cord pH.

CONCLUSIONS

Umbilical cord blood lactate is a reliable marker for intrapartum fetal asphyxia compared to cord acid-base status with better prediction for newborns with low Apgar score.

The reliability of foetal blood sampling as a test of foetal acidosis in labour

OBJECTIVES

To establish whether foetal blood sampling for pH is a reliable test of foetal acidosis in labour by comparing paired foetal blood samples taken at a single procedure.

STUDY DESIGN

We conducted a prospective study assessing 293 consecutive attempts at foetal blood sampling in labour over a four month period from February to May 2012. A total of 100 paired samples were suitable for analysis. We compared the consistency of pH results of paired foetal blood samples, evaluated cases where inconsistent results would result in conflicting clinical decisions, and explored factors associated with discordant results.

RESULTS

There was a statistically significant difference between the mean pH of the two samples: 7.297 (SD 0.065) versus 7.315 (SD 0.059), p<0.0005. Of the 100 paired samples, 43 had a difference greater than the laboratory acceptable maximum analytical difference of 0.038. There was discordance between the samples in 16 cases with results crossing a decision threshold, and in 11 cases (69%) delivery was by emergency caesarean section. Inconsistent results were not associated with specific clinical factors and occurred more often with senior operators.

CONCLUSION

Foetal blood sampling is considered by many as the gold standard in assessing intrapartum foetal wellbeing. We have demonstrated inconsistency of paired foetal blood pH results which suggests that foetal blood sampling should not be considered infallible.

Comparison of two point-of-care testing (POCT) devices for fetal lactate during labor

BACKGROUND

Point-of-care testing (POCT) of fetal scalp blood lactate is used as an alternative for pH analysis. Lactate measurements have not been standardized and values vary with each device used. The aim of this study was to evaluate the performance of two POCT lactate meters for intrapartum use.

METHODS

Analytical performance of StatStrip Lactate (Nova Biomedical) and Lactate Pro (Arkray) was evaluated using CLSI EP10. Both POCT meters were compared with our lactate reference method (RapidLab 860; Siemens Healthcare Diagnostics) using fetal scalp and neonatal cord blood. Deming regression analysis was performed.

RESULTS

StatStrip Lactate coefficients of variation (CVs) were 5.1%, 5.0% and 2.6% at 0.9, 7.5 and 14.1 mmol/L lactate, respectively. CVs for Lactate Pro were 10.7%, 5.2% and 5.7% at 1.7, 4.1 and 6.4 mmol/L lactate, respectively. Consecutive lactate measurements in 37 fetal scalp and 122 cord blood samples revealed different test characteristics for the two POCT devices. In fetal scalp blood: StatStrip Lactate=1.13*RapidLab-0.39 (R(2)=0.907) and Lactate Pro=0.95*RapidLab-0.03 (R(2)=0.823). In cord artery blood: StatStrip Lactate=1.08*RapidLab-0.09 (R(2)=0.810) and Lactate Pro=0.72*RapidLab+0.59 (R(2)=0.807).

CONCLUSIONS

Overall performance of both Lactate Pro and StatStrip Lactate was good, with StatStrip Lactate having smallest CVs and closest correlation to our reference method. Both StatStrip Lactate and Lactate Pro can be used as a lactate POCT device for obstetric use.

Is intrapartum fetal blood sampling a gold standard diagnostic tool for fetal distress?

Developed in 1960s, cardiotocography is a screening test and fetal blood sampling (FBS) is an adjunctive, diagnostic technique to detect fetal hypoxia. A fetal blood sample pH value of less than 7.20 has a higher specificity than a pathological CTG to predict low Apgar score at 1 min. Though with a pathological CTG and despite a normal FBS pH value the risk of delivering a hypoxic infant is 30-50%, FBS has assumed considerable importance in purportedly reducing unnecessary obstetric intervention. The evidence for this is weak: the use of FBS with CTG has been shown to reduce operative vaginal deliveries though not Caesarean sections due to fetal distress. There is no difference in the umbilical artery pH at delivery with the use of intermittent FBS with CTG compared to CTG alone. FBS is an invasive procedure: obtaining an adequate blood sample is often difficult and the pH results are affected by handling of the sample, aerobic contamination and processing. Validation of intrapartum FBS requires that the pH and other values obtained are compared to a 'gold standard' technique. Although FBS has been compared to other tests such as scalp lactate, pulse oximetry, fetal ECG waveform analysis, and central haemodynamics in labouring rhesus monkeys, none of these can be considered as 'gold standard'. In the light of the existing evidence, the role of intrapartum FBS as a gold standard diagnostic technique is unproven.

SIMULATION TRAINING FOR OBSTETRIC PROCEDURES AND EMERGENCIES

The World Health Organisation (WHO) has estimated that 1500 women die every day from preventable complications of pregnancy and childbirth. While barriers to accessing healthcare are undoubtedly multi-factorial, studies have repeatedly shown that providing skilled healthcare workers can result in untold benefits for women and babies in developing countries. The phenomenon of preventable maternal and fetal morbidity and mortality is not limited to the developing world. The Confidential Enquiries into Maternal Deaths (CEMD) and Stillbirths and Infant Deaths (CESDI) in the UK have repeatedly identified substandard care as a major contributor to maternal and neonatal mortality. In 2008 The King's Fund publishedSafe Births: Everybody's business,an independent enquiry into the safety of maternity services in England. This recommended that simulation-based training to assess clinical, communication and team skills should be available to all maternity staff, and that training should form a core activity. Many hospitals in the UK have been running in-house courses for staff for over a decade with measurable improvements in neonatal outcomes. The value of these training schemes is recognised and rewarded through reduced insurance premiums for participating hospital trusts as part of clinical negligence schemes. Gaining competence in managing obstetric emergencies presents particular challenges for trainees. Most emergencies are, thankfully, uncommon but some constitute life-threatening events where management naturally falls to the most experienced available clinician. The skills required are often particular to emergencies and therefore novel to trainees. Utilising emergencies as training opportunities is further complicated by the presence of a conscious patient.

Management of foetal asphyxia by intrauterine foetal resuscitation

Management of foetal distress is a subject of gynaecological interest, but an anaesthesiologist should know about resuscitation, because he should be able to treat the patient, whenever he is directly involved in managing the parturient patient during labour analgesia and before an emergency operative delivery. Progressive asphyxia is known as foetal distress; the foetus does not breathe directly from the atmosphere, but depends on maternal circulation for its oxygen requirement. The oxygen delivery to the foetus depends on the placental (maternal side), placental transfer and foetal circulation. Oxygen transport to the foetus is reduced physiologically during uterine contractions in labour. Significant impairment of oxygen transport to the foetus, either temporary or permanent may cause foetal distress, resulting in progressive hypoxia and acidosis. Intrauterine foetal resuscitation comprises of applying measures to a mother in active labour, with the intention of improving oxygen delivery to the distressed foetus to the base line, if the placenta is functioning normally. These measures include left lateral recumbent position, high flow oxygen administration, tocolysis to reduce uterine contractions, rapid intravenous fluid administration, vasopressors for correction of maternal hypotension and amnioinfusion for improving uterine blood flow. Intrauterine Foetal Resuscitation measures are easy to perform and do not require extensive resources, but the results are encouraging in improving the foetal well-being. The anaesthesiologist plays a major role in the application of intrauterine foetal resuscitation measures.

Determination of pH or lactate in fetal scalp blood in management of intrapartum fetal distress: randomised controlled multicentre trial

OBJECTIVE

To examine the effectiveness of pH analysis of fetal scalp blood compared with lactate analysis in identifying hypoxia in labour to prevent acidaemia at birth.

DESIGN

Randomised controlled multicentre trial.

SETTING

Labour wards.

PARTICIPANTS

Women with a singleton pregnancy, cephalic presentation, gestational age >or=34 weeks, and clinical indication for fetal scalp blood sampling.

INTERVENTIONS

Standard pH analysis (n=1496) or lactate analysis (n=1496) with an electrochemical microvolume (5 mul) test strip device. The cut-off levels for intervention were pH <7.21 and lactate >4.8 mmol/l, respectively.

MAIN OUTCOME MEASURE

Metabolic acidaemia (pH <7.05 and base deficit >12 mmol/l) or pH <7.00 in cord artery blood.

RESULTS

Metabolic acidaemia occurred in 3.2% in the lactate group and in 3.6% in the pH group (relative risk 0.91, 95% confidence interval 0.61 to 1.36). pH <7.00 occurred in 1.5% in the lactate group and in 1.8% in the pH group (0.84, 0.47 to 1.50). There was no significant difference in Apgar scores <7 at 5 minutes (1.15, 0.76 to 1.75) or operative deliveries for fetal distress (1.02, 0.93 to 1.11).

CONCLUSION

There were no significant differences in rate of acidaemia at birth after use of lactate analysis or pH analysis of fetal scalp blood samples to determine hypoxia during labour.

TRIAL REGISTRATION

ISRCT No 1606064.

Cohort study of the decision to delivery interval and neonatal outcome for emergency operative vaginal delivery

OBJECTIVE

The purpose of this study was to assess whether a target decision to delivery interval (DDI) is appropriate for 'emergency' operative vaginal delivery and whether this would reduce adverse neonatal outcomes.

STUDY DESIGN

We performed a retrospective cohort study of 1021 singleton term babies who experienced operative delivery for 'fetal distress' in the second stage of labor between 1998 and 2003 in Dundee, Scotland.

RESULTS

The mean DDI in a labor room was 14.5 minutes (SD 9.5) compared to 30.0 minutes (SD 14.6) in an operating room. Shorter DDIs were associated with use of local rather than regional or general anesthesia. There were no significant differences in rates of low Apgar score (< 7 at 5 min) OR 0.99 (95% CI 0.27, 3.71), fetal acidosis (pH < 7.10) OR 1.24 (0.78, 1.99), neonatal resuscitation OR 1.00 (95% CI 0.65, 1.53), or admission to NICU OR 0.53 (95% CI 0.27, 1.03) for babies delivered within 15 minutes compared to greater than 15 minutes. The outcomes were similar for a 30-minute threshold. The DDIs for forceps and vacuum deliveries were similar as were neonatal outcomes.

CONCLUSION

A DDI of 15 minutes is an achievable target for operative vaginal delivery in a labor room with 30 minutes for delivery in an operating room; however, setting arbitrary limits is unlikely in itself to prevent adverse neonatal outcomes.