IUGR Management
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Direct answer
A fetus whose estimated weight falls below the 10th centile for gestational age has fetal growth restriction (IUGR when placental insufficiency is proven by abnormal growth velocity or Doppler); symmetric restriction — small head and abdomen together, starting early — points to intrinsic fetal causes (aneuploidy, TORCH infection, genetic syndromes), while asymmetric restriction — an abdomen lagging behind a spared head after 28 weeks — points to uteroplacental failure, the pattern of hypertensive disease, anaemia, malnutrition and smoking that dominates Indian practice. Surveillance is Doppler-led: umbilical artery waveforms are the primary tool, and management follows the waveform — normal flow with normal growth means continued watchfulness, reduced end-diastolic flow means intensified monitoring, and absent or reversed end-diastolic flow mandates admission, steroids, and usually delivery once corticosteroids have matured the lungs.
What you must remember
- Definitions: estimated fetal weight below the 10th centile; "severe" commonly below the 3rd centile; IUGR implies a pathological process behind a small fetus, while some small fetuses are constitutionally healthy (a distinction the exam notes via normal growth velocity and normal Dopplers).
- Symmetric (about 20-30 per cent): head and abdomen proportionately small, onset before 20-24 weeks — causes include chromosomal anomaly, first-trimester TORCH, constitutional; Dopplers usually normal.
- Asymmetric (70-80 per cent): placental insufficiency after 28 weeks with brain-sparing blood diversion — abdomen lags (liver stores shrink), head relatively preserved, raised head-to-abdomen circumference ratio, and falling end-diastolic flow in the umbilical artery.
- Maternal causes to hunt: hypertensive disease, severe anaemia, malnutrition, chronic disease, malaria and other Indian-context infections, smoking, and multiple pregnancy; fetal causes: aneuploidy, TORCH, structural anomaly; placental causes include infarction, chronic abruption, velamentous cord insertion and a single umbilical artery.
- Surveillance toolkit: growth scan with Dopplers every 2 weeks (interval growth matters more than one snapshot), umbilical artery systolic-diastolic ratio as the core index, middle cerebral artery flow rising with brain sparing, and CTG or biophysical profile for current status.
- Action thresholds: absent end-diastolic flow before about 32-34 weeks — admit, steroids, consider delivery; reversed end-diastolic flow — deliver (caesarean often, as fetuses tolerate labour poorly); reduced flow before 37 weeks — watch closely and deliver by 37-38 weeks; normal Dopplers with normal fluid — follow to term.
- At delivery: continuous electronic fetal monitoring in labour (a growth-restricted placenta decompensates fast), paediatric team present, delayed cord clamping balanced against the need for resuscitation, and placental histopathology where possible.
Doppler-directed timing of delivery
Picture a 26-year-old, anaemic and mildly hypertensive, whose 30-week scan shows an abdominal circumference below the 3rd centile with normal head growth and deepest vertical pocket of 3 cm. The umbilical artery systolic-diastolic ratio is raised but end-diastolic flow is present, and the middle cerebral artery shows increased flow — asymmetric restriction with early brain sparing. The plan: correct her anaemia and blood pressure, betamethasone 12 mg IM two doses for fetal lungs, and scans with Dopplers twice weekly.
Three weeks later the pathway forks. If flow remains merely reduced and growth velocity holds, she is watched to 37 weeks and delivered then, vaginally if the trace stays healthy. If the next Doppler shows absent end-diastolic flow, she is admitted, steroids are completed, and delivery is planned around 32-34 weeks in most protocols — by caesarean, because the compromised fetus has no reserve for labour contractions. If reversed flow or a deteriorating biophysical profile appears before steroid completion, delivery happens anyway with neonatal unit backup, weighing the risk of hypoxia against prematurity. The organising principle, and the sentence worth carrying into the exam, is that the umbilical artery Doppler — not the estimated weight centile — times the delivery of the growth-restricted fetus; weight tells you the size, Doppler tells you the safety.
Examiners love thresholds
The confusion harvested here is centile versus criterion: below the 10th centile defines smallness, but timing decisions hang on end-diastolic flow. The second favourite is pattern recognition from a scan report — head sparing with a high head-to-abdomen ratio is placental asymmetry; both small together at 20 weeks with normal Dopplers points fetal, and the next investigation is karyotype and TORCH serology, not more Dopplers. Third, the ISTH of the topic: absent or reversed end-diastolic flow with a non-reassuring CTG is the caesarean answer, every time.
Frequently asked questions
How is asymmetric IUGR distinguished from symmetric?
Asymmetric restriction spares the head while the abdomen lags (high head-to-abdomen ratio), begins late, and reflects placental insufficiency; symmetric restriction affects both measurements from early pregnancy and suggests intrinsic fetal causes.
Which investigation is the mainstay of IUGR surveillance?
Umbilical artery Doppler — the systolic-diastolic ratio and end-diastolic flow pattern, repeated with growth scans every two weeks.
What does absent or reversed umbilical end-diastolic flow demand?
Admission, completion of antenatal corticosteroids, and delivery — usually by caesarean and commonly by 32-34 weeks for absent flow, sooner for reversed flow with other warning signs.
What causes symmetric fetal growth restriction?
Early-onset intrinsic pathology — fetal aneuploidy, TORCH infection, genetic syndromes and constitutional smallness — with Dopplers typically normal.
Why does the growth-restricted fetus need continuous monitoring in labour?
A placenta already failing at rest cannot oxygenate the fetus through contractions, so the risk of abrupt decelerations and acidosis is high.