Overview & Scope

• • Definitions

    • SGA (Small for Gestational Age):
      Estimated fetal weight (EFW) or abdominal circumference (AC) <10th centile.

    • Severe SGA: EFW or AC <3rd centile.

    • Fetal Growth Restriction (FGR): Failure to reach growth potential due to pathology (placental insufficiency, maternal disease, genetic, etc.).

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    🔹 Risk Factors

    • Maternal: previous SGA/IUGR, smoking, cocaine, extremes of maternal age, low BMI, chronic disease (hypertension, diabetes, renal, SLE, thrombophilia).

    • Pregnancy-related: abnormal uterine artery Doppler at 20–24 weeks, PET, APH.

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    🔹 Screening

    • Universal fundal height measurement from 24 weeks (plot on customised growth charts).

    • Serial growth scans for high-risk women (usually 2–4 weekly).

    • Uterine artery Doppler at 20–24 weeks for women with major risk factors.

    • Symphysio-fundal height (SFH):

      • For low-risk pregnancies from 24 weeks.

      • Plot on customized growth chart.

    • Ultrasound biometry:

      • For high-risk women or if SFH < expected.

      • Use customized growth charts (GROW charts).

        Investigations (when SGA or IUGR suspected)

        • Confirm fetal wellbeing and cause:

          • Umbilical artery Doppler — most important test.

          • If abnormal → add middle cerebral artery (MCA) Doppler, uterine artery Doppler, and CPR (cerebroplacental ratio).

        • Exclude other causes:

          • Fetal anomaly scan, infection screen (CMV, toxoplasmosis, syphilis if indicated), karyotyping if early or severe.

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    🔹 Diagnosis (Ultrasound)

    • Biometry: EFW, AC.

    • Liquor: oligohydramnios supports diagnosis.

    • Doppler studies:

      • Umbilical artery (UA):

        • Raised PI = placental resistance.

        • AEDF/REDF = severe placental disease.

      • Middle cerebral artery (MCA): Brain-sparing if low PI.

      • Cerebroplacental ratio (CPR): MCA PI / UA PI <1 = high risk.

      • Ductus venosus (DV): Abnormal if advanced compromise (predicts fetal acidaemia).

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    Adjunctive Management

    • Low-dose aspirin (75–150 mg daily) from ≤16 weeks for high-risk women — reduces risk of FGR and pre-eclampsia.

    • No evidence for bed rest, oxygen therapy, or nutritional supplements.

    🔹 Management

    • Maternal lifestyle: Smoking cessation, control chronic disease, aspirin (for PET prevention if risk factors).

    • Low-dose aspirin (150 mg daily from 12–36 wks) if risk factors for PET/IUGR.

    • Do not use: bed rest, oxygen, sildenafil, nutritional supplements (no proven benefit).

    • Surveillance:

      • SGA with normal Dopplers → repeat scans 2–3 weekly.

      • Abnormal Dopplers → increase monitoring (weekly or more).

      • If UA AEDF/REDF → admit, steroids, daily CTG/Doppler.

      • Use UA Doppler as primary surveillance tool.

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    🔹 Timing of Delivery

    • SGA with normal UA Doppler → deliver at 37 weeks.

    • SGA with abnormal UA Doppler but present diastolic flow → deliver at 37 weeks.

    • SGA with absent/reversed end-diastolic flow (AEDF/REDF) →

      • ≥32 weeks → deliver after steroids.

      • <32 weeks → individualise; continue close monitoring if DV normal, but deliver if DV abnormal/CTG pathological.

    • Severe SGA (<3rd centile or EFW <500g at viability) → poor prognosis; counsel parents.

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    🔹 Mode of Delivery

    • Normal Dopplers → IOL with continuous CTG reasonable.

    • Abnormal Dopplers (especially AEDF/REDF) → usually caesarean section.

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    🔹 Key Exam Pearls (MRCOG traps)

    • Umbilical artery Doppler = best surveillance tool.

    • MCA and DV are adjuncts, not first-line.

    • Aspirin is preventive, not curative.

    • Symphyseal-fundal height (SFH) has poor sensitivity but is used for low-risk women.

    • Delivery timing is the most tested SBA area: remember 37 weeks for normal UA Doppler SGA, earlier if abnormal.