Assessment of fetal growth in twin pregnancies

M R C O G PA R T 2 · S O S P O C K E T C A R D · K N O W L E D G E A R E A 5 – A N T E N ATA L C A R E

Assessment of Fetal Growth in Twin Pregnancies: Evidence-Based Practice Prasad S, Khalil A. Assessment of fetal growth in twin pregnancies: evidence-based practice. TOG 2026;28:30–49. doi:10.1111/tog.70019

2–4% ×2 ~40% OF ALL BIRTHS ARE TWINS STILLBIRTH RISK VS SINGLETONS TWINS MISCLASSIFIED SGA AT 35 WKS (SINGLETON CHARTS)

DO N' T-M IS S FA C TS

  1. Chorionicity by 11+0–13+6 weeks; scan MCDA 2-weekly from 16 wks, DCDA 4-weekly from 20 wks

  2. Discordance = (EFW larger − EFW smaller) ÷ EFW larger × 100. RCOG/NICE 25%, ACOG 20%, ESPRIT 18%; ≤10% physiological

  3. Delphi sFGR: EFW <3rd centile alone; else ≥2 of EFW <10th, discordance ≥25%, UA-PI >95th (+ AC <10th in MC only)

  4. Gratacós: I positive EDF → birth 34+0–35+6 wks; II persistent AREDF and III intermittent AREDF → birth by 32 wks (RCOG)

  5. Type III → sudden intrauterine demise and neurological injury in the LARGER co-twin

  6. Early-onset sFGR <24 wks: demise risk up to 20%. Late-onset ≥24 wks: surveil for TAPS

  7. Singleton charts overcall SGA: 17% vs 8% (Shea); ~40% misclassified at 35 wks → iatrogenic preterm birth, no benefit

  8. Twin stillbirth risk is double singletons (MBRRACE-UK 2021); DC sFGR is managed as per singleton FGR protocols

WHO SAYS WHAT

ISUOG / FIGO / SOGC: use (or consider) twin-specific charts ACOG & SMFM: no specific chart recommendation

RCOG & ISUOG: Gratacós classification incorporated FERN study: awaited — early-onset MC FGR

ABBREVIATION KEY

AA — arterio-arterial (anastomosis) FMF — Fetal Medicine Foundation

AC — abdominal circumference GA — gestational age

ACOG — American College of Obstetricians and Gynecologists HFEA — Human Fertilisation and Embryology Authority

AREDF — absent/reversed end-diastolic flow ISUOG — International Society of Ultrasound in Obstetrics and Gynaecology AUC — area under the curve IVF — in vitro fertilisation BMI — body mass index MBRRACE-UK — Mothers and Babies: Reducing Risk through CPR — cerebroplacental ratio Audits and Confidential Enquiries across the UK CTG — cardiotocography MC / MCDA — monochorionic / monochorionic diamniotic DC / DCDA — dichorionic / dichorionic diamniotic NICE — National Institute for Health and Care Excellence DV — ductus venosus NICHD — (US) National Institute of Child Health and Human EFW — estimated fetal weight Development FERN — Fetal Growth Restriction in Twins study NICU — neonatal intensive care unit FGR — fetal growth restriction OR — odds ratio FIGO — International Federation of Gynaecology and Obstetrics RCOG — Royal College of Obstetricians and Gynaecologists sFGR — selective fetal growth restriction STORK — Southwest Thames Obstetric Research Collaborative

SGA — small for gestational age TAPS — twin anaemia–polycythaemia sequence

SMFM — Society for Maternal–Fetal Medicine TTTS — twin-to-twin transfusion syndrome

SOGC — Society of Obstetricians and Gynaecologists of Canada UA-PI — umbilical artery pulsatility index

Source: The Obstetrician & Gynaecologist (TOG), RCOG journal — doi:10.1111/tog.70019

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