SUMMARY:

SMFM has released guidance on fetal growth restriction (FGR), an evidence-based document that provides a standardized approach to diagnosis and management. The document emphasizes the importance of FGR as a significant pregnancy complication that

…occurs in up to 10% of pregnancies and is second to premature birth as a cause of infant morbidity and mortality. In addition to its significant perinatal impact, FGR also has an impact on long-term health outcomes

• Diagnosis of FGR and Definitions
• FGR Workup
• Fetal Assessment
• FGR Prevention and Treatment
• FGR Delivery Timing

Diagnosis of FGR and Definitions

ACOG FGR Definition

• FGR: EFW <10th percentile for gestational age
• Small for gestational age (SGA): Newborn birthweight <10th percentile for gestational age

SMFM FGR Definition

• SMFM supports the above ACOG definitions
• SMFM also includes AC<10th percentile for gestational age for FGR diagnosis
  • Screening performance similar between EFW and AC (see ‘Related ObG Topics’ below)

Note: The term ‘IUGR’ should no longer be used | SMFM document, based on more recent evidence, does not consider symmetric vs asymmetric FGR to be helpful in determining prognosis

Early onset FGR: <32 weeks

• More severe disease course and more likely to be associated with
  • Placental insufficiency
  • Hypertensive disorders
  • Genetic disorders
  • Maternal hypertension
  • Doppler abnormalities

Late onset of FGR ≥32 weeks

• Accounts for 70-80% cases
  • Generally, milder clinical course and without flow abnormalities

Severe FGR

• EFW <3rd percentile
• Consistent with a more severe form of FGR

KEY POINTS:

FGR Workup

• Detailed ultrasound
  • Strong association with fetal anomalies and/or chromosomal disorders (20%)
  • Detailed ultrasound CPT code: 76811
• Genetics and fetal diagnostic testing: Chromosomal Microarray Analysis (see ‘Related ObG Topics’ below) is indicated for the following
  • FGR <32 weeks
  • FGR and polyhdramnios and/or fetal malformation are detected regardless of gestational age
• Viral work-up
  • CMV testing
    • Associated with isolated FGR | However, routine testing not recommended due to low CMV incidence
    • Offer CMV (PCR) if patient undergoing amniocentesis
  • Toxoplasmosis, rubella, or herpes and isolated FGR
    • Routine screening is not recommended unless other risk factors are identified

Fetal Assessment

NST (Cardiotocography [CTG])

• Weekly NSTs after viability
• Increase frequency if warranted based on Doppler abnormalities or other clinical indications (e.g. comorbidities or risk factors)
• SMFM addresses BPP in the statement and finds that “further studies are required to prove usefulness of BPP”

Umbilical Artery (UA) Doppler Measurement

• Normal flow measurements
  • UA Dopplers every 1 to 2 weeks
• Abnormal end diastolic velocity (EDV)
  • Decreased EDV (flow ratios >95th percentile) or FGR <3rd percentile: Weekly Dopplers
  • Absent end diastolic velocity (AEDV): 2 to 3 times/week
  • Reversed end diastolic velocity (REDV)
    • Hospitalize
    • Administer antenatal corticosteroids
    • Perform NST 1 to 2 times/day | Low threshold for delivery depending on clinical scenario

Note: SMFM recommends against routine use of ductus venosus dopplers, middle cerebral artery dopplers, or uterine artery Doppler studies in early or late onset FGR | These studies have not been found to lead to improved accuracy over umbilical artery dopplers

FGR Prevention and Treatment

Prevention

• Due to lack of evidence, SMFM recommends against the use of the following for prevention of FGR
  • Prenatal aspirin (conflicting data including negative result in ASPRE trial)
  • LMWH

Treatment

• SMFM recommends against the use for treatment of FGR
  • Sildenafil
  • Activity restriction

FGR Delivery Timing

• With oligohydramnios: 34w0d to 37w6d
• Normal UA Doppler and EFW 3 to 10th percentile: 38 to 39 weeks
• EFW <3rd percentile (severe FGR): 37 weeks
• Decreased UA flow (S/D, RI, or PI > 95 percentile): 37 weeks
• AEDV: 33 to 34 weeks
• REDV: 30 to 32 weeks

Fetal Growth Restriction: Mode of Delivery

• Cesarean delivery
  • No strict recommendation for cesarean delivery based on FGR alone
  • Reserve for usual fetal and maternal indications
• Mode of delivery for most cases of severe FGR with umbilical artery changes (AEDV or REDV): Cesarean delivery for fetal indication
• Mode of delivery should be determined on a case-by-case basis, taking in to account clinical presentation and maternal preferences

FGR and Preterm

• Administer corticosteroids and magnesium sulfate as per current guidelines

Learn More – Primary Sources:

SMFM Consult Series 52: Diagnosis and Management of Fetal Growth Restriction

Related ObG Topics: