Lucan · Conditions

Intrapartum fetal surveillance

Australian guidance: RANZCOG C-Obs 1 Intrapartum Fetal Surveillance (Mar 2026)

1. Definition and epidemiology

Intrapartum fetal surveillance (IFS) refers to the monitoring of foetal wellbeing during labour with the aim of detecting foetal hypoxia early enough to allow intervention before irreversible harm occurs. The principal aim is to prevent adverse perinatal outcomes arising from severe or sustained foetal hypoxia related to labour. Unexpected intrapartum stillbirth is rare in high-income countries; neonatal encephalopathy (NE) occurs at approximately 1.6 per 1,000 live births in high-income regions and carries a high risk of perinatal mortality or long-term neurological sequelae including cerebral palsy. Approximately 10% of neonatal deaths in infants born from 32 weeks gestational age may be attributed to hypoxic ischaemic encephalopathy (HIE), a cause-specific subset of neonatal encephalopathy.

2. Pathophysiology

Normal foetal physiology allows the foetus to tolerate a transient degree of hypoxia during labour through redistribution of cardiac output and a shift to anaerobic metabolism. When hypoxia is severe or prolonged, compensatory mechanisms are overwhelmed and metabolic acidosis develops. Lactic acid accumulates as anaerobic glycolysis becomes the predominant energy source, and the base excess falls (a base deficit in arterial blood is the direct indicator of metabolic acidosis). Acidosis impairs myocardial contractility and leads to multiorgan dysfunction. The foetal brain is especially vulnerable because of its high metabolic demand and limited glycogen stores. Robbins (Ch 22) describes hypoxic ischaemic injury as producing neuronal necrosis in watershed zones, with periventricular leukomalacia seen in premature infants and parasagittal cortical injury in term infants. The resultant neonatal encephalopathy reflects the degree and duration of the hypoxic insult and has a direct causal pathway to cerebral palsy and neurodevelopmental disability.

3. Clinical presentation and diagnostic criteria

Women at risk of intrapartum foetal compromise may present with antepartum or intrapartum risk factors identified at admission or during labour. On history, clinicians should elicit antepartum risks including gestational hypertension or preeclampsia, gestational diabetes mellitus on treatment or with foetal macrosomia, antepartum haemorrhage, previous intrapartum stillbirth, and prolonged pregnancy at or beyond 41 weeks. Intrapartum features raising concern include abnormal vaginal bleeding, clinical chorioamnionitis, meconium-stained amniotic fluid, preterm labour under 37 weeks, prolonged first stage, and excessive uterine activity (tachysystole, hypertonus, or hyperstimulation). On examination, uterine contraction frequency, duration, and rest intervals should be documented alongside foetal heart rate (FHR) characteristics. A comprehensive risk assessment at admission and continuously throughout labour is required; it must integrate the maternal condition, labour progress, clinical examination findings, and the FHR pattern over time.

4. Investigations and AU-specific cutoffs

The primary investigation is foetal heart rate monitoring, performed either by intermittent auscultation (IA) or continuous cardiotocography (CTG). For women without identified risk factors, IA using Doppler or Pinard is appropriate. Continuous CTG should be offered when risk factors are present antenatally, at labour onset, or during labour.

CTG features associated with low probability of foetal compromise include a stable baseline rate of 110 to 160 beats per minute (bpm), baseline variability of 6 to 25 bpm, accelerations of at least 15 bpm lasting at least 15 seconds, no decelerations, and non-excessive uterine activity. Features unlikely to be associated with foetal compromise in isolation include a baseline rate of 100 to 109 bpm, reduced or reducing variability of 3 to 5 bpm for up to 40 minutes, absence of accelerations in the preceding hour, early decelerations, and uncomplicated variable decelerations. Features that may indicate foetal compromise and require further action include baseline tachycardia greater than 160 bpm, rising baseline FHR, complicated variable decelerations, late decelerations, and prolonged decelerations lasting more than 90 seconds and up to 5 minutes. Features likely to be associated with foetal compromise and requiring immediate management include bradycardia lasting more than 5 minutes, absent baseline variability below 3 bpm, increased variability above 25 bpm, a sinusoidal pattern, complicated variable decelerations with reduced or absent baseline variability, and late decelerations with reduced or absent baseline variability.

When the CTG is abnormal but immediate birth is not required, fetal blood sampling (FBS) can be performed. Scalp lactate is preferred over scalp pH as it is easier to obtain and more affordable for most units. Fetal scalp stimulation is an alternative when FBS is contraindicated or unavailable; an acceleration or improved variability in response to stimulation is reassuring. FBS is contraindicated at less than 34 weeks gestation, with non-vertex presentation, or in the presence of maternal blood-borne viral infection.

5. Management

Management begins with a comprehensive risk assessment at admission and is dynamic throughout labour. Informed consent and discussion of monitoring options should begin in the third trimester and be revisited at admission and as clinical circumstances change.

When the FHR pattern is considered abnormal, immediate management options include initiating or maintaining continuous CTG, repositioning the woman to avoid aortocaval or cord compression, ceasing or reducing oxytocin if excessive uterine activity is the likely cause, administering tocolysis if excessive uterine activity is driving the abnormality, correcting maternal hypotension and rehydrating with intravenous fluid, and timely escalation to the most senior clinician available. If a significant abnormality persists, further foetal evaluation including FBS or expedited birth is warranted.

When continuous foetal monitoring is indicated but external CTG is difficult, a fetal scalp electrode (FSE) should be used if not contraindicated. FSE is contraindicated with placenta praevia, face or unknown presentation, and in the context of maternal blood-borne viral infections. Routine admission CTG is not recommended for women without risk factors given its limited clinical benefit and association with increased caesarean birth rates.

6. Pharmacology and AU PBS notes

There is no specific PBS-listed pharmacotherapy for intrapartum foetal surveillance itself. Tocolysis is used as a temporising measure when excessive uterine activity is the cause of an abnormal FHR pattern, or to reduce foetal hypoxia while arranging expedited birth. Due to insufficient evidence to determine the safest and most effective agent, clinicians should follow their institutional protocol for acute tocolysis. Commonly used agents in Australian practice include terbutaline (a beta-2 agonist) and glyceryl trinitrate (GTN) given sublingually. Absolute contraindications to tocolysis include drug allergy, suspected placental abruption, suspected uterine rupture, relevant maternal medical conditions, and fluid overload. Oxytocin (Syntocinon in AU) used for labour augmentation should be ceased or reduced promptly when uterine hyperstimulation is identified as contributing to foetal compromise.

7. Complications and monitoring

The principal complication of unrecognised or inadequately managed intrapartum foetal hypoxia is neonatal encephalopathy, which carries a high risk of perinatal death, cerebral palsy, and long-term neurodisability. Additional neonatal complications include multiorgan dysfunction affecting the kidneys, myocardium, liver, and haematological system.

Paired umbilical cord blood gas or lactate analysis should be performed at births where there was evidence of intrapartum foetal compromise or poor neonatal condition, defined by an Apgar score below 4 at 1 minute or below 7 at 5 minutes, an abnormal intrapartum CTG not normalised prior to birth, or an assisted or unplanned caesarean birth undertaken for foetal compromise. Consideration of paired cord blood gas at all births is also reasonable as routine practice. Clinicians providing intrapartum care should maintain regular training in CTG interpretation through programs such as the Fetal Surveillance Education Program (FSEP), as participation improves CTG knowledge and may improve neonatal outcomes. Each institution should maintain standardised clinical protocols for response to abnormal intrapartum FHR patterns, and healthcare services should address human factors including fatigue, communication, and escalation pathways.

Written for Australian practice and grounded in the guidance named above. Study material only — not medical advice. Always check against current guidelines.