Multiple Pregnancy · sFGR
sFGR — Selective Fetal Growth Restriction in Twins
When one twin isn't growing properly. Gratacos classification I-III by UA Doppler. ~10-25% of monochorionic twins. Different from TTTS. Delivery timing by type. RCOG Green-top 51.
Last reviewed 2 June 2026
What is sFGR?
Selective fetal growth restriction. One twin not growing properly while the other is. ~10-25% of monochorionic; ~25% of dichorionic.
Criteria: EFW of one twin <10th centile + >25% growth discordance.
Gratacos classification
Based on UA Doppler of smaller twin:
- Type I: positive end-diastolic flow throughout. Mildest.
- Type II: persistent AEDF / REDF.
- Type III: intermittent AEDF / REDF (cyclic). Worst prognosis — unpredictable.
sFGR vs TTTS
- TTTS: blood flow imbalance via placental connections; fluid + bladder changes.
- sFGR: growth discordance; unequal placental territory.
Can coexist. Different treatments.
Delivery timing
- Type I: 34-36 weeks if stable.
- Type II: 32-34 weeks.
- Type III: 30-32 weeks; earlier if signs of compromise.
Steroids preceding. Magnesium <32 wk. Usually C-section.
Monitoring
- Weekly-fortnightly ultrasound from diagnosis.
- EFW for each twin separately.
- Doppler studies (UA, MCA, CPR, DV).
- BPP if concerns.
- CTG monitoring.
Bigger twin risks
- Co-twin demise: if smaller twin dies, larger has 10-30% brain injury / death risk (MC twins especially).
- Preterm birth.
- Haemodynamic effects in MC twins.
- Psychosocial effects on parents.
Laser surgery for sFGR?
- Dichorionic: not relevant (no shared circulation).
- MC with intermittent AEDF/REDF: laser may protect larger twin; smaller may die.
- Bipolar cord coagulation: occludes smaller twin’s cord — extreme decision; protects larger twin.
Ethical + emotional implications profound. Specialist counselling.
Catch-up growth
Smaller twin usually catches up over months-years. By age 2-3, most sFGR twins reach similar size + development. Neurodevelopment generally good with appropriate care.
Future pregnancies
- PE-related recurrence: ~25-50%.
- Idiopathic recurrence: ~20-30%.
- If next pregnancy singleton, MC twin-specific issue unlikely to recur.
- Preconception consultation valuable.
Different scenarios
Scenario 1: MC twins, sFGR Type I at 28 wk, both stable
Fortnightly scans. Deliver 34-36 wk planned. Both usually OK.
Scenario 2: Type III sFGR, intermittent REDF at 30 wk
Admit. Daily monitoring. Steroids + magnesium. Deliver within days usually.
Scenario 3: DC twin sFGR, smaller twin stable
Outpatient monitoring. Deliver 36-37 wk. Twins likely separate placental issues.
Scenario 4: Co-twin demise at 26 wk MC twins
Surviving twin urgent assessment; MRI 4-6 wk for brain injury; preterm delivery often follows; bereavement support.
Scenario 5: Severe Type II/III at 24 wk, considering laser
Specialist fetal medicine. Ethical + family counselling. Bipolar cord coagulation option discussed.
Care guidance — sFGR
- Every-2-week MC twin scans from 16 wk picks up sFGR early.
- Specialist fetal medicine for MC twins.
- Type-based delivery timing.
- Steroids if preterm.
- Magnesium <32 wk.
- Twins Trust (TAMBA) + BLISS UK support.
- Mental health support — high anxiety pregnancies.
- Long-term developmental follow-up for both twins.
Sources
- Gratacos E, et al. A classification system for selective intrauterine growth restriction in monochorionic pregnancies. UOG 2007.
- RCOG Green-top Guideline 51. Management of monochorionic twin pregnancy.
- NICE NG137. Twin and triplet pregnancy.
- Twins Trust (TAMBA). twinstrust.org.
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Frequently asked questions
What is sFGR?
SELECTIVE FETAL GROWTH RESTRICTION — one twin in a TWIN pregnancy is not growing properly while the other is. AFFECTS: ~10-25% of MONOCHORONIC twin pregnancies (identical, sharing placenta); ~25% in DICHORONIC (separate placentas). MORE SERIOUS in monochorionic — placental sharing means problems for one affects both. CRITERIA: EFW of one twin <10th centile + >25% growth discordance between twins. DIFFERENT from TTTS (twin-twin transfusion — see /calculators/ttts-quintero).
How is sFGR classified?
GRATACOS CLASSIFICATION based on UMBILICAL ARTERY (UA) DOPPLER of the smaller twin: TYPE I: positive end-diastolic flow throughout pregnancy; mildest. TYPE II: ABSENT or REVERSED end-diastolic flow (AEDF/REDF) — persistent. TYPE III: INTERMITTENTLY absent/reversed flow ('cyclic' pattern). TYPE III WORST PROGNOSIS — unpredictable; sudden fetal deterioration possible. CLASSIFICATION INFORMS monitoring frequency + delivery timing.
What's the difference between sFGR and TTTS?
(1) TTTS: BLOOD FLOW imbalance between twins via placental vessel connections; FLUID changes (oligo + polyhydramnios); BLADDER changes. (2) sFGR: GROWTH discordance; ONE twin smaller; PLACENTAL territory unequal (one twin's share much smaller). DIFFERENT PATHOPHYSIOLOGY. CAN COEXIST. DIFFERENT TREATMENTS: TTTS → laser surgery; sFGR → monitoring + delivery timing (laser sometimes for severe Type II/III).
How is sFGR monitored?
(1) WEEKLY-FORTNIGHTLY ultrasound from diagnosis; (2) GROWTH (EFW) for each twin separately; (3) DOPPLER STUDIES: UA for both twins; MCA; CPR; sometimes DV for compromised twin; (4) BPP if concerns; (5) CTG monitoring; (6) FREQUENCY scales with severity: Type I — every 2 wk; Type II/III — weekly or more. SPECIALIST fetal medicine team. INPATIENT in severe cases.
When is delivery planned?
(1) TYPE I: usually deliver 34-36 weeks if otherwise stable; (2) TYPE II: typically 32-34 weeks; (3) TYPE III: 30-32 weeks often (more unpredictable); EARLIER if signs of compromise. ALL: steroids preceding; magnesium if <32 wk; usually CAESAREAN delivery; specialist neonatal team. INDIVIDUALISED based on Doppler trajectory, growth velocity, parental wishes.
Will the bigger twin be ok?
USUALLY YES. RISKS to the larger twin: (1) CO-TWIN DEMISE — if smaller twin dies, larger twin has 10-30% risk of brain injury (cerebral palsy) or death; (2) PRETERM BIRTH — delivery for smaller twin affects larger; (3) HAEMODYNAMIC effects in MC twins; (4) PSYCHOSOCIAL effects on parents. MOST CASES: both twins survive with planned delivery + good outcomes. RARE: one twin dies in utero despite all efforts.
What about laser surgery for sFGR?
SOMETIMES considered for SEVERE Type II/III. (1) DICHORIONIC twins: laser not relevant (no shared circulation). (2) MONOCHORIONIC sFGR with intermittent AEDF/REDF: LASER ABLATION to separate circulations may protect larger twin from co-twin demise effects; smaller twin may die from intervention. (3) BIPOLAR CORD COAGULATION: actively occludes smaller twin's cord — extreme decision when smaller twin won't survive anyway + protects larger twin. ETHICAL + EMOTIONAL implications profound. SPECIALIST fetal medicine + family counselling.
What if one twin doesn't survive?
MONOCHORIONIC: surviving twin at risk of brain injury (10-30%) from acute haemodynamic shifts at moment of co-twin demise. CAREFUL surveillance of surviving twin; MRI 4-6 weeks after; ongoing developmental tracking. DICHORIONIC: surviving twin less affected; preterm birth common after fetal demise. EMOTIONAL impact severe — Sands UK + Twins Trust offer specialist bereavement support. CHILD GROWING UP with knowledge of twin loss needs gentle awareness.
How are babies born after sFGR?
USUALLY C-SECTION especially if Type II/III or preterm. VAGINAL POSSIBLE in selected cases (twin 1 cephalic, no other complications). STEROIDS preceding any preterm delivery. MAGNESIUM if <32 wk. NEONATAL TEAM prepared for both babies — small twin needs more support usually. BIGGER TWIN often does well. SEPARATION possible if one twin needs intensive care unit; other rooming with mum.
Will the babies catch up?
OFTEN YES. SMALLER twin catches up over months-years usually. BY AGE 2-3, MOST sFGR twins reach similar size + development as larger twin. SOME persistent difference. NEURODEVELOPMENT generally good with appropriate care. SUPPORT: BLISS for NICU babies; Twins Trust (TAMBA) UK; HIE-specific support if applicable; developmental follow-up.
What's the prognosis?
TYPE I: ~85-95% both twins survive; minimal long-term effects usually. TYPE II: ~75-90% both twins; some risk co-twin demise; preterm complications. TYPE III: ~50-80% both twins; highest unpredictability; sudden deterioration possible. INDIVIDUAL CASE depends on: chorionicity; gestation at diagnosis; growth trajectory; timing of intervention; postnatal care quality. MOST FAMILIES have both babies surviving + thriving.
Can sFGR be prevented?
USUALLY NOT — placental development factor. RISK REDUCTION: (1) ROUTINE antenatal care; (2) STOP smoking; (3) ASPIRIN from <16 wk if other PE risk factors; (4) ADDRESSING chronic conditions pre-pregnancy. SCREENING: monochorionic twin scans every 2 weeks from 16 weeks pick up sFGR early. PROACTIVE management improves outcomes.
Will future pregnancies have sFGR?
RECURRENCE depends on cause: (1) PE-related: ~25-50%; aspirin from <16 wk next pregnancy. (2) IDIOPATHIC: ~20-30% recurrence. (3) MONOCHORIONIC twin-specific issue: less likely to recur if next pregnancy singleton. PRECONCEPTION CONSULTATION valuable. SUBSEQUENT TWIN pregnancy: serial growth scans from 16 weeks.
What about emotional support?
TWIN PREGNANCY with complications very stressful. (1) BIRTH PLANNING anxieties; (2) UNCERTAINTY about outcomes; (3) NICU separation challenges; (4) BONDING with two babies of different needs; (5) GUILT / GRIEF if one twin lost or affected; (6) PARENT INFANT mental health team referral. SUPPORT: BLISS (sick/preterm babies), Twins Trust (TAMBA), Sands (bereavement), perinatal mental health, sibling support if family has older children.
How does this relate to other calculators on BumpBites?
Companion: /calculators/ttts-quintero; /calculators/twin-probability; /calculators/ua-dv-doppler; /calculators/cpr-doppler; /calculators/cervical-length; /calculators/antenatal-steroids; /calculators/magnesium-sulphate; /calculators/biophysical-profile.