Clinical overview
Fetal monitoring is the art of inferring an invisible patient's wellbeing from indirect signals — and the central exam skill is not knowing how each test works but knowing which test answers which question, what each can and cannot tell you, and how the answer changes management. No single method is "best": each trades sensitivity against specificity, cost against availability, and the chronic question ("is this placenta failing over days to weeks?") against the acute question ("is this fetus coping with labour right now?"). A registrar who can compare the methods — and match the method to the clinical question and the level of care — is doing exactly what this HOTS objective demands.
The hard truth that frames the whole topic is that most fetal monitoring tests are good at ruling out compromise (high negative predictive value, reassuring you) and poor at ruling it in (low positive predictive value, lots of false alarms). The cardiotocograph (CTG) is the classic example: a normal trace is genuinely reassuring, but an abnormal trace mostly reflects a healthy fetus mounting a normal reflex response, not impending death. This asymmetry is why monitoring done indiscriminately on low-risk women causes harm — it drives caesareans and instrumental births without reducing cerebral palsy or perinatal death — while the same tool, applied to the right high-risk fetus, is genuinely protective. In the South African context, where the NDoH National Integrated Maternal and Perinatal Care Guideline (NDoH, 2024) governs practice, and where intrapartum hypoxia and antepartum stillbirth remain major contributors to perinatal mortality (per the Saving Mothers / NCCEMD and perinatal-care surveillance), choosing and interpreting these tests correctly is a life-and-death registrar competency.
Core knowledge
The two clinical questions
Antenatal and intrapartum monitoring answer fundamentally different questions, and confusing them is a classic exam error.
- Antenatal: Is chronic uteroplacental insufficiency present, and is the fetus deteriorating over days to weeks? The threats are placental insufficiency, growth restriction and chronic hypoxia. You have time; you are surveilling.
- Intrapartum: Is the fetus tolerating the acute, repetitive hypoxic stress of contractions over minutes to hours? Each contraction transiently reduces placental perfusion; a fetus with reserve copes, one without reserve decompensates. You are watching for acute decompensation in real time.
The physiology underpinning both is covered in contractions-fetal-oxygenation and placental-insufficiency-response; the fetal compensatory cascade — redistribution of blood to brain, heart and adrenals ("brain-sparing"), then loss of that compensation — is what every test is trying to detect at successively later or earlier stages.
Figure I16.1 — Monitoring-method map matching antenatal and intrapartum tests to the clinical question, risk status and level of care.
Antenatal methods compared
Maternal perception of fetal movements is the cheapest, most universal "monitor" and the one most relevant at primary-care level. It costs nothing, needs no equipment, and a sudden reduction is a recognised harbinger of stillbirth. Its weakness is poor specificity and reliance on maternal report; formal "kick-count" charts have not been shown to reduce stillbirth in trials and are not mandated, but any woman reporting reduced fetal movements (RFM) warrants assessment (see decreased-fetal-movements and RCOG GTG 57).
Symphysis-fundal height (SFH) measurement with a plotted growth chart is the antenatal screening backbone in low-resource settings. It is cheap and ubiquitous but operator-dependent and insensitive (it detects perhaps half of small-for-gestational-age fetuses). A static or falling SFH is a trigger to escalate to ultrasound, not an endpoint in itself.
Ultrasound biometry (estimated fetal weight, abdominal circumference) is the reference standard for detecting the small fetus and distinguishing constitutionally small from growth-restricted (see intrauterine-growth-restriction and RCOG GTG 31). It diagnoses the problem but does not by itself time delivery — for that you need the dynamic tests below.
Doppler velocimetry is the pivotal antenatal surveillance tool in the growth-restricted fetus. Umbilical artery Doppler reflects placental resistance: rising resistance, then absent, then reversed end-diastolic flow marks worsening placental failure and is the only fetal test repeatedly shown to reduce perinatal death in high-risk (FGR) pregnancies. Middle cerebral artery (MCA) Doppler detects brain-sparing redistribution; a falling cerebroplacental ratio (CPR) is an earlier sign in late-onset FGR. Ductus venosus (DV) Doppler is a late, ominous sign reflecting cardiac decompensation and helps time delivery in early-onset FGR. The integrated use of these — and the ISUOG Doppler standards — is summarised below.
Biophysical profile (BPP) combines a CTG with four ultrasound parameters (fetal breathing, gross movement, tone, amniotic fluid volume), each scored 0 or 2 (max 10). It integrates acute markers (the first three are reflexes lost early in hypoxia) with a chronic marker (oligohydramnios reflects sustained redistribution away from the kidneys — see liquor-volume-abnormalities). It is resource- and time-intensive and its routine use is not supported by strong outcome trials, so in practice a "modified BPP" (CTG + amniotic fluid) or Doppler-led surveillance is more common.
Antenatal CTG (the "non-stress test") records the fetal heart against accelerations and movements. A reactive trace is reassuring; in isolation it has not been shown to reduce stillbirth and is best used as one input rather than a standalone screen.
Figure I16.2 — Doppler-led FGR surveillance showing the progression from placental resistance to brain-sparing, late decompensation and timed delivery.
Intrapartum methods compared
Intermittent auscultation (IA) — with a Pinard stethoscope or hand-held Doppler — is the recommended default for low-risk labour both internationally (NICE NG235, Intrapartum care, 2023) and in SA. Auscultate for 1 minute immediately after a contraction, at set intervals (classically every 15 minutes in the first stage and every 5 minutes / after each contraction in the second stage — standard teaching). Its strengths are that it keeps the woman mobile, supports physiological labour, and avoids the false positives of continuous CTG. Its limitation is that it samples rate and gross decelerations but cannot show variability or the morphology of decelerations.
Continuous electronic fetal monitoring (CTG) records the fetal heart rate continuously against the tocograph (contractions). It is the tool for high-risk labour — its purpose is to detect emerging intrapartum hypoxia early enough to act. The evidence (a long-standing Cochrane synthesis of the early RCTs) is sobering and examinable: compared with IA, continuous CTG in low-risk labour roughly halves neonatal seizures but does not reduce cerebral palsy or perinatal mortality, while increasing caesarean and instrumental delivery rates. Hence: CTG for indicated (high-risk) labour, IA for low-risk. SA and UK guidance is explicit that continuous CTG should be started for new intrapartum risk factors. Interpretation, categorisation and the "DR C BRAVADO" structure are taught in ctg-interpretation; this chapter is about choosing CTG, not reading it.
Fetal blood sampling (FBS) for scalp pH/lactate is the classic second-line adjunct to a pathological CTG — it converts a low-specificity warning into an objective measure of acid–base status, reducing unnecessary intervention. It requires dilatation, ruptured membranes, equipment and skill, carries practical and infection considerations (a relative contraindication in untreated HIV/hepatitis), and is unavailable at most SA district facilities — so for the SA registrar, the realistic second-line is usually expedited delivery, not FBS.
Fetal scalp stimulation (an acceleration in response to digital stimulation during a vaginal exam) is a free, immediate bedside surrogate: an acceleration is reassuring and broadly correlates with a non-acidotic fetus, making it the practical "FBS substitute" where sampling is unavailable.
Computerised CTG / STAN (ST-analysis of the fetal ECG) and other adjuncts exist but have not consistently improved outcomes over good standard CTG interpretation and are not part of routine SA practice — know that they exist and that the evidence is equivocal.
Comparison tables
| Method | Question answered | Best use | Key strength | Key limitation |
|---|---|---|---|---|
| Fetal movements / RFM | Acute or chronic compromise? | All pregnancies; RFM triage | Free, universal | Subjective; charts unproven |
| SFH + growth chart | Is the fetus small? | Antenatal screening (district) | Cheap, ubiquitous | Insensitive, operator-dependent |
| Ultrasound biometry | Is the fetus growth-restricted? | Confirm/quantify SGA | Reference standard for size | Diagnoses, doesn't time delivery |
| Umbilical artery Doppler | Placental resistance/failure | FGR surveillance | Only test proven to cut perinatal death in FGR | Needs ultrasound + skill |
| MCA Doppler / CPR | Brain-sparing redistribution | Late-onset FGR | Earlier than UA in late FGR | Late-changing alone |
| Ductus venosus Doppler | Cardiac decompensation | Timing delivery in early FGR | Late, specific danger sign | Very late marker |
| Biophysical profile | Composite acute + chronic | Selected high-risk surveillance | Integrates several axes | Time/resource heavy; weak trial base |
| Intermittent auscultation | Coping with contractions? | Low-risk labour (default) | Mobility, fewer false positives | No variability/morphology |
| Continuous CTG | Coping with contractions? | High-risk labour | High NPV; halves neonatal seizures | False positives → more CS; no ↓ CP/mortality |
| Fetal blood sampling | True acid–base status? | 2nd line to pathological CTG | Objective pH/lactate | Equipment/skill; HIV caution; rarely available in SA |
| Late-onset FGR (≥32 wk) | Early-onset FGR (<32 wk) |
|---|---|
| Often subtle, normal UA Doppler | UA Doppler abnormal early |
| CPR / MCA changes lead | DV and CTG short-term variation lead |
| Deterioration over days | Compensation can hold for weeks then collapse |
| Deliver near term once surveillance abnormal | Balance prematurity vs hypoxia; corticosteroids, MgSO₄ neuroprotection |
Assessment
The assessment skill is matching the method to the question, the risk and the level of care.
Step 1 — risk-stratify. Decide whether this is a low-risk or high-risk pregnancy/labour (see high-risk-pregnancy-risks). Low-risk antenatal women need movement awareness, SFH plotting and routine ultrasound; low-risk labour needs intermittent auscultation. High-risk pregnancies (hypertension/pre-eclampsia, diabetes, FGR, post-dates, reduced movements, antepartum haemorrhage, previous stillbirth, multiple pregnancy) earn intensified surveillance and continuous intrapartum CTG.
Step 2 — choose the antenatal tool to the question. Is the fetus small? → biometry. Is the small fetus deteriorating, and when do I deliver? → Doppler (umbilical first, then MCA/CPR and DV per gestation and the early- vs late-onset pattern above), supplemented by liquor assessment and short-term-variation CTG. Use gestational-age-assessment to anchor every interpretation — a chart is only as good as its dates.
Step 3 — at the onset of and during labour, reassess continually. Both NICE NG229 (Fetal monitoring in labour, 2022) and SA practice frame intrapartum monitoring as continual risk assessment, not a one-off decision. A woman may begin in the IA pathway and cross to continuous CTG the moment a new risk factor appears: fresh meconium-stained liquor, maternal pyrexia ≥38°C, tachysystole (>5 contractions in 10 minutes) or any contraction lasting ≥2 minutes, fresh bleeding, abnormal auscultation findings, oxytocin augmentation, or epidural insertion. Auscultate after — not during — a contraction, for a full minute, and document the rate and any decelerations against the partogram / WHO Labour Care Guide.
Step 4 — when CTG is abnormal, escalate the assessment. A non-reassuring or pathological CTG is a prompt to act, not merely to keep watching: identify and treat reversible causes (position, hypotension after epidural, excessive oxytocin, dehydration, pyrexia), and where available use fetal scalp stimulation or FBS to clarify; where not (most SA district settings), escalate toward expedited delivery. Always interpret the trace in the whole clinical picture — gestation, growth, liquor, the stage and progress of labour, and maternal condition — never as an isolated tracing.
Management
Management means converting the monitoring answer into a timed action, calibrated to the SA level of care.
Antenatal pathway
- Reassuring surveillance (normal growth velocity, normal Doppler, normal liquor, normal movements): continue routine antenatal care at the appropriate level; do not over-investigate the well, well-grown fetus.
- Abnormal surveillance: escalate the frequency and modality of monitoring and refer up a level. A growth-restricted fetus with rising umbilical artery resistance needs serial Doppler at a regional/tertiary unit, antenatal corticosteroids if <34 weeks (RCOG GTG 74), magnesium sulphate for neuroprotection where very preterm delivery is anticipated, and a planned delivery timed to the worsening Doppler pattern — DV changes or abnormal short-term variation force delivery in early-onset FGR; abnormal CPR/MCA and term-proximity drive delivery in late-onset FGR.
- Reduced fetal movements: assess promptly with CTG ± ultrasound (growth, liquor, Doppler) per RCOG GTG 57; a normal assessment is reassuring but recurrent RFM lowers the threshold for delivery near term.
Intrapartum pathway
- Low-risk labour: intermittent auscultation throughout, with continual reassessment.
- High-risk labour: continuous CTG from the outset, with structured interpretation and categorisation (ctg-interpretation).
Intrapartum emergency drill — acute fetal compromise / "fetal bradycardia"
A sustained deep deceleration or bradycardia (fetal heart rate below ~100 bpm for ≥3 minutes) is an obstetric emergency. Act immediately and in parallel:
- CALL FOR HELP — summon senior obstetric, midwifery, anaesthetic and neonatal teams; declare the emergency out loud.
- EXCLUDE AND TREAT THE CATASTROPHE — perform a vaginal examination to exclude cord prolapse (RCOG GTG 50) and rapid progress; consider abruption and uterine rupture (uterine-rupture, especially with a previous scar) and scar dehiscence.
- INTRAUTERINE RESUSCITATION — turn the woman to the left lateral position; give a rapid IV fluid bolus; stop oxytocin; consider acute tocolysis for tachysystole; correct hypotension (treat post-epidural hypotension). Maternal facial oxygen is of unproven benefit and not routinely recommended — prioritise the manoeuvres above.
- THE 3-MINUTE RULE — if the bradycardia does not recover, prepare for immediate delivery. Standard teaching is to deliver by the quickest safe route if recovery has not begun by ~3 minutes and is not achieved by ~9 minutes — operative vaginal delivery if the criteria are met (instrumental-delivery), otherwise category-1 caesarean with a decision-to-delivery target of 30 minutes.
- PREPARE NEONATAL RESUSCITATION — have the trained team and equipment ready (neonatal-resuscitation).
Figure I16.3 — Intrapartum monitoring escalator from low-risk intermittent auscultation to continuous CTG, abnormal-trace escalation and the fetal bradycardia drill.
SA level-of-care reality
The honest comparison must include availability. At district (level 1) facilities, the realistic toolkit is fetal-movement awareness, SFH, intermittent auscultation, often a CTG machine, and limited or no Doppler/FBS. Regional (level 2) and tertiary (level 3) units add ultrasound, Doppler, BPP and, where staffed, FBS. The management implication is that the district-level registrar's most important "monitoring" skill is recognising when surveillance has exceeded the facility's capacity and arranging timely referral — a Doppler-indicated FGR or a labour needing FBS belongs at a higher level. In HIV-positive women on suppressive ART (TLD per the SA HIV/ART Consolidated Guidelines, 2023) routine monitoring is unchanged; in untreated or unknown-status women, invasive monitoring (FBS, fetal scalp electrode) carries a vertical-transmission consideration and is best avoided in favour of external monitoring and stimulation.
Red flags / pitfalls
- Monitoring the low-risk woman as if she were high-risk. Routine continuous CTG in low-risk labour increases caesareans and instrumental births without reducing cerebral palsy or death — it is a recognised harm. Use IA for low-risk labour.
- Reading the CTG in isolation. A trace means little without gestation, growth, liquor, labour progress and maternal status. Acting on a pathological trace alone, without excluding cord prolapse, abruption or rupture, is dangerous.
- Treating an abnormal CTG as a reason to keep watching rather than to act. Non-reassuring traces are a prompt for intrauterine resuscitation and escalation, not passive observation.
- Over-trusting the positive, under-trusting the negative. Remember the asymmetry: most tests have high NPV and low PPV. A reassuring result is genuinely reassuring; an abnormal one is usually a false alarm — but you cannot afford to miss the rare true positive.
- Using kick-count charts as a safety net. They have not reduced stillbirth; do not let a "normal chart" override a mother's report of reduced movements.
- Forgetting the dates. Every growth chart, Doppler reference range and BPP score is gestation-dependent; uncertain dating undermines all of it.
- Invasive monitoring in untreated HIV. Avoid fetal scalp electrodes and FBS where maternal HIV is untreated or unknown.
- Assuming a tool exists. Don't build a management plan around Doppler or FBS at a facility that has neither — escalate and refer.
- Tachysystole from oxytocin. Excessive uterine activity is a common, reversible cause of fetal compromise; reassess and reduce/stop oxytocin before assuming intrinsic fetal disease.
Evidence anchors
- NDoH National Integrated Maternal and Perinatal Care Guideline (NDoH, 2024) — SA source of truth for antenatal and intrapartum monitoring, levels of care and referral.
- Saving Mothers / NCCEMD (latest triennium) and perinatal-care surveillance — intrapartum hypoxia and stillbirth burden in SA.
- NICE NG235 — Intrapartum care (2023) — intermittent auscultation as the low-risk default.
- NICE NG229 — Fetal monitoring in labour (2022) — continual risk assessment; triggers for continuous CTG (meconium, pyrexia ≥38°C, tachysystole >5/10 or contractions ≥2 min); simplified CTG categorisation; pairs with FIGO CTG and the WHO Labour Care Guide (2020).
- NICE NG201 — Antenatal care (2021) — antenatal surveillance framework.
- RCOG GTG 31 — Small-for-Gestational-Age and Growth-Restricted Fetus + ISUOG Doppler standards (umbilical/MCA/ductus venosus, cerebroplacental ratio) — Doppler-led FGR surveillance; umbilical artery Doppler reduces perinatal death in high-risk pregnancy.
- RCOG GTG 57 — Reduced Fetal Movements — assessment of RFM.
- RCOG GTG 50 — Umbilical Cord Prolapse and RCOG GTG 74 — Antenatal Corticosteroids — relevant to the intrapartum emergency and timed preterm delivery.
- ILCOR 2025 CoSTR / ERC 2025 Newborn Life Support / AAP NRP (8th ed) — neonatal resuscitation readiness after acute compromise.
- SA HIV/ART Consolidated Guidelines (2023) — invasive-monitoring caution in untreated/unknown HIV.