Predictive value of a fetal heart rate acceleration at the time of fetal blood sampling in labour

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.

Fetal scalp stimulation test: an adjunct to intermittent auscultation in non-reassuring fetal status during labor

AIMS

To evaluate fetal scalp stimulation test (FSST) as an adjunct to intermittent auscultation in diagnosis of intrapartum fetal acidosis and associate result of FSST with cord blood pH and immediate neonatal outcome.

MATERIAL & METHODS

This study was conducted at a tertiary hospital in India. Digital FSST was performed in seven hundred and fifty women in labor with singleton gestation ≥37 weeks, cephalic presentation and fetal heart abnormalities and/or thick meconium stained amniotic fluid. Intermittent auscultation was used for fetal monitoring during labor. The outcome measure was cord blood pH < 7.20 and neonatal morbidity.

RESULTS

The non-reactive FSST is associated with lower umbilical cord blood pH, lower Apgar scores and higher asphyxia related neonatal morbidity (P-value < 0.001). The non-reactive FSST had 41% sensitivity and 84% specificity to detect pH < 7.20. The positive predictive value of FSST for fetal acidosis is 44% and negative predictive value is 83%. The likelihood ratio for acidosis with noncreative FSST is 2.57.

CONCLUSIONS

Non-reactive FSST is associated with adverse neonatal outcomes. The positive and negative predictive values of FSST to diagnose fetal cord blood pH < 7.20 during labor are 44% & 83%, respectively.

The importance of ‘awareness’ for understanding fetal pain

Our understanding of when the fetus can experience pain has been largely shaped by neuroanatomy. However, completion of the cortical nociceptive connections just after mid-gestation is only one part of the story. In addition to critically reviewing evidence for whether the fetus is ever awake or aware, and thus able to truly experience pain, we examine the role of endogenous neuro-inhibitors, such as adenosine and pregnanolone, produced within the feto-placental unit that contribute to fetal sleep states, and thus mediate suppression of fetal awareness. The uncritical view that the nature of presumed fetal pain perception can be assessed by reference to the prematurely born infant is challenged. Rigorously controlled studies of invasive procedures and analgesia in the fetus are required to clarify the impact of fetal nociception on postnatal pain sensitivity and neural development, and the potential benefits or harm of using analgesia in this unique setting.

Vibroacoustic and scalp stimulation

Both VAS and scalp stimulation are useful in the evaluation of fetal compromise by decreasing the number of falsely abnormal FHR tests and limiting the number of unnecessary interventions, thus improving the efficiency of antepartum and intrapartum FHR monitoring. As is true for all types of fetal assessment using FHR monitoring, VAS and scalp stimulation have limitations, and a lack of response to these methodologies does not necessarily indicate fetal acidemia. When either VAS or scalp stimulation is employed, one must take into consideration their respective predictive values (see Table 1). Fetal VAS or scalp stimulation should be considered as one facet of comprehensive fetal evaluation. When these techniques are used in this manner, the clinician evaluating the fetus in the antepartum or intrapartum period may prevent unnecessary intervention and improve maternal and neonatal outcome.

Fetal heart rate changes and cerebral oxygenation measured by near-infrared spectroscopy during the first stage of labour

OBJECTIVE

To determine the relationship between contraction related changes in fetal heart rate and cerebral oxygenation measured by near-infrared spectroscopy during labour.

STUDY DESIGN

A specially designed optical probe was inserted through the dilated cervix and placed against the fetal head in 30 women during labour. Alterations in fetal heart rate during the final hour of the first stage of labour were compared with changes in the cerebral haemoglobin oxygenation index (delta oxyhaemoglobin concentration - delta deoxyhaemoglobin concentration) measured before, during and after uterine contractions.

RESULTS

Uterine contractions which were associated with either no alteration, accelerations or early decelerations of the fetal heart rate showed no significant changes in the haemoglobin oxygenation index. Variable, late and prolonged decelerations all showed significant decreases in the haemoglobin oxygenation index (P < 0.01) either during (variable) or after (variable, late and prolonged) the uterine contraction.

CONCLUSION

The association between variable, late and prolonged FHR decelerations and significant falls in cerebral oxygenation during late labour suggests that these fetal heart rate patterns are associated with an increased risk of fetal cerebral hypoxia.