Fetal Growth Restriction Guidelines

Definition and Diagnostic Criteria

Fetal growth restriction should be defined as an ultrasonographic estimated fetal weight (EFW) or abdominal circumference (AC) below the 10th percentile for gestational age using population-based references such as Hadlock, as recommended by the American College of Obstetricians and Gynecologists 1, 2

Early-onset FGR is diagnosed before 32 weeks of gestation, typically more severe with substantial placental implantation abnormalities and elevated hypoxia, according to the American College of Obstetricians and Gynecologists 2
Late-onset FGR is diagnosed at or after 32 weeks, associated with milder placental deficiencies and lower perinatal morbidity, as stated by the American College of Obstetricians and Gynecologists 2

Severe FGR is defined as EFW below the 3rd percentile, which carries increased risk of adverse perinatal outcomes regardless of Doppler findings, as reported by the American College of Obstetricians and Gynecologists 2
High-risk FGR is defined as EFW <3rd centile OR abnormal umbilical artery (UA), uterine artery, middle cerebral artery (MCA), or cerebroplacental ratio (CPR) Doppler, according to the American College of Obstetricians and Gynecologists 3, 4

The American College of Obstetricians and Gynecologists recommends low-dose aspirin (100-150 mg daily) should be initiated before 16 weeks of gestation in women with major risk factors for placental insufficiency, including prior preeclampsia <34 weeks or prior FGR <5th centile 3, 4, 5, 6
Aspirin is more effective when started at ≤16 weeks and at doses of 100 mg compared to 60 mg, as stated by the American College of Obstetricians and Gynecologists 3, 5
The American College of Obstetricians and Gynecologists recommends that low-molecular-weight heparin should not be used solely for prevention of recurrent FGR 1
The American College of Obstetricians and Gynecologists recommends that sildenafil or activity restriction should not be used for in utero treatment of FGR 1
Smoking cessation at any stage of pregnancy is universally recommended by the American College of Obstetricians and Gynecologists 3, 4, 7, 5, 6

The American College of Obstetricians and Gynecologists recommends that a detailed obstetrical ultrasound examination should be performed with early-onset FGR (<32 weeks) 1, 2
Accurate pregnancy dating using first-trimester crown-rump length is essential before diagnosing FGR, as stated by the American College of Obstetricians and Gynecologists 2
EFW is generated using regression equations combining biparietal diameter, head circumference, AC, and femur length, according to the American College of Obstetricians and Gynecologists 2

Once FGR is diagnosed, serial umbilical artery Doppler assessment must be performed to assess for deterioration, as recommended by the American College of Obstetricians and Gynecologists 1, 8, 2
Normal UA Doppler should be performed every 2 weeks, as stated by the American College of Obstetricians and Gynecologists 5, 6
Decreased end-diastolic velocity (flow ratios >95th percentile) or severe FGR (EFW <3rd percentile) should be performed weekly, according to the American College of Obstetricians and Gynecologists 1, 2
Absent end-diastolic velocity should be performed 2-3 times per week, as recommended by the American College of Obstetricians and Gynecologists 1, 2, 9
Reversed end-diastolic velocity requires hospitalization, administration of antenatal corticosteroids, and heightened surveillance, as stated by the American College of Obstetricians and Gynecologists 1

The American College of Obstetricians and Gynecologists recommends delivery timing based on EFW percentile and Doppler findings for late-onset FGR (≥32 weeks) 2, 9
EFW 3rd-10th percentile with normal UA Doppler requires delivery at 38-39 weeks, as stated by the American College of Obstetricians and Gynecologists 2, 9
Decreased diastolic flow OR severe FGR requires delivery at 37 weeks, according to the American College of Obstetricians and Gynecologists 2
Absent end-diastolic velocity requires delivery at 33-34 weeks, as recommended by the American College of Obstetricians and Gynecologists 2
Reversed end-diastolic velocity requires delivery at 30-32 weeks, as stated by the American College of Obstetricians and Gynecologists 2

The American College of Obstetricians and Gynecologists recommends universal agreement to administer antenatal corticosteroids before delivery at <34 weeks 7, 10, 8
Some guidelines extend to 35+6 weeks, as stated by the American College of Obstetricians and Gynecologists 6
The American College of Obstetricians and Gynecologists recommends that magnesium sulfate should be used for neuroprotection in early-onset FGR (<32 weeks) 7, 10, 8, 9

The American College of Obstetricians and Gynecologists recommends umbilical artery Doppler assessment as the first-line surveillance tool in all suspected Fetal Growth Restriction (FGR) cases, with surveillance frequency based on Doppler findings 11
In late-onset FGR (>32 weeks), cerebral Doppler studies (middle cerebral artery and cerebroplacental ratio) can be used to influence surveillance and delivery timing, as recommended by the American Journal of Obstetrics and Gynecology 11
The American Journal of Obstetrics and Gynecology suggests that guidelines show inconsistency in recommended frequency (2-4 weeks) for growth monitoring, but consensus favors 2-3 week intervals 11

The American College of Obstetricians and Gynecologists recommends against relying solely on fundal height in obese patients, and instead suggests using ultrasound scans, as fundal height measurements are unreliable 12
The American Journal of Obstetrics and Gynecology suggests that delaying delivery in severe FGR may be harmful, as evidence suggests delivery at 38 weeks in suspected FGR may be optimum unless there are earlier concerns about fetal well-being 12