Guidelines for Assessing and Managing Estimated Fetal Weight (EFW)

Diagnostic Criteria and Assessment

The American College of Obstetricians and Gynecologists recommends that fetal growth restriction (FGR) be defined as an ultrasonographic EFW or abdominal circumference (AC) below the 10th percentile for gestational age 1
Population-based fetal growth references should be used in determining fetal weight percentiles, with the American College of Obstetricians and Gynecologists citing the importance of accurate pregnancy dating 1, 2
Accurate pregnancy dating is an essential prerequisite for diagnosing FGR, with first-trimester crown-rump length being the most reliable method, according to the American College of Obstetricians and Gynecologists 3
Ultrasonographic EFW is generated using regression equations that combine biometric measurements of fetal biparietal diameter, head circumference, abdominal circumference, and femur length, as recommended by the American College of Obstetricians and Gynecologists 3

When FGR is diagnosed, a detailed obstetrical ultrasound examination should be performed, particularly with early-onset FGR, as recommended by the American College of Obstetricians and Gynecologists 1, 2
Fetal diagnostic testing, including chromosomal microarray analysis, should be offered when FGR is detected with fetal malformation, polyhydramnios, or both, regardless of gestational age, according to the American College of Obstetricians and Gynecologists 1
Prenatal diagnostic testing with chromosomal microarray analysis should be offered when unexplained isolated FGR is diagnosed at <32 weeks of gestation, as recommended by the American College of Obstetricians and Gynecologists 1

Early-onset FGR is diagnosed before 32 weeks of gestation, while late-onset FGR is diagnosed at or after 32 weeks, with the American College of Obstetricians and Gynecologists noting that early-onset FGR is typically more severe 3, 4
An EFW below the 3rd percentile is associated with increased risk of adverse perinatal outcome regardless of umbilical and middle cerebral artery Doppler indices, according to the American College of Obstetricians and Gynecologists 3
The presence of abnormal umbilical artery Doppler indices predicts adverse perinatal outcomes, as noted by the American College of Obstetricians and Gynecologists 3

Once FGR is diagnosed, serial umbilical artery Doppler assessment should be performed to assess for deterioration, as recommended by the American College of Obstetricians and Gynecologists 1, 5
For pregnancies with decreased end-diastolic velocity or severe FGR, weekly umbilical artery Doppler evaluation is recommended, according to the American College of Obstetricians and Gynecologists 1
When umbilical artery absent end-diastolic velocity is detected, Doppler assessment should be performed 2-3 times per week, as recommended by the American College of Obstetricians and Gynecologists 1, 6

For pregnancies with FGR and normal umbilical artery Doppler when EFW is between 3rd and 10th percentile, delivery at 38-39 weeks of gestation is suggested, according to the American College of Obstetricians and Gynecologists 2
For pregnancies with FGR and decreased diastolic flow or with severe FGR, delivery at 37 weeks of gestation is recommended, as noted by the American College of Obstetricians and Gynecologists 2
For pregnancies with FGR and absent end-diastolic velocity, delivery at 33-34 weeks of gestation is recommended, according to the American College of Obstetricians and Gynecologists 2
For pregnancies with FGR and reversed end-diastolic velocity, delivery at 30-32 weeks of gestation is recommended, as recommended by the American College of Obstetricians and Gynecologists 2

The fetal biometry set for estimating fetal weight should include biparietal diameter, head circumference, abdominal circumference, and femur length, as recommended by the studies published in Hypertension (2018)【7】【8】.

Small‑for‑gestational‑age is defined as an estimated fetal weight below the 10th percentile for gestational age, according to the same Hypertension (2018) sources【7】【8】.

Birth weight must be recorded within 24 hours of delivery using a calibrated electronic scale with a resolution of 10 g, as stipulated in Human Reproduction Update (2020)【9】【10】.

Implementation of quality‑assurance programs for ultrasound measurements is essential to maintain accuracy, as highlighted in Human Reproduction Update (2020)【10】.