What is the normal estimated fetal weight (EFW) for a fetus at 35 weeks gestational age?

Normal Estimated Fetal Weight at 35 Weeks Gestation

At 35 weeks gestational age, a normal estimated fetal weight (EFW) is defined as being at or above the 10th percentile for gestational age, which typically corresponds to approximately 2,000–2,800 grams depending on the growth reference used.

Understanding Normal Fetal Weight Parameters

The 10th percentile threshold is the critical diagnostic boundary that distinguishes normal fetal growth from fetal growth restriction (FGR). According to the Society for Maternal-Fetal Medicine, a fetus is considered to have normal growth when the EFW or abdominal circumference is at or above the 10th percentile for gestational age 1, 2.

Weight Range Expectations at 35 Weeks

• Median fetal weight at 35 weeks is approximately 2,400–2,600 grams based on population-based growth references 3
• The 10th percentile at 35 weeks typically falls around 2,000–2,100 grams 3
• The 3rd percentile (severe growth restriction threshold) is approximately 1,800–1,900 grams at this gestational age 1

Clinical Significance of Growth Percentiles

Normal Growth (≥10th Percentile)

• Fetuses with EFW at or above the 10th percentile have baseline perinatal risks comparable to the general obstetric population 1
• These pregnancies typically proceed to routine term delivery at 39–40 weeks without additional surveillance 2

Below Normal Thresholds

• EFW between 3rd–10th percentile: Stillbirth rate approximately 1.5%, which is twice that of normally growing fetuses 1, 2
• EFW below 3rd percentile: Stillbirth rate increases to 2.5%, representing severe FGR regardless of Doppler findings 1

Important Clinical Caveats

Accuracy of Ultrasound Estimation

• Ultrasound EFW has inherent measurement variability, with a median absolute percentage difference of approximately 9–10% from actual birth weight 4, 5
• Formulas tend to overestimate weight in small-for-gestational-age fetuses and underestimate in larger fetuses 4, 5
• Multiple biometric parameters (biparietal diameter, head circumference, abdominal circumference, femur length) improve accuracy compared to single measurements 1

Prerequisites for Accurate Assessment

• Accurate pregnancy dating is mandatory before interpreting EFW percentiles; dating should be established by first-trimester crown-rump length measurement 1, 2
• Population-based growth references (such as Hadlock curves) are recommended over customized charts for diagnostic consistency 1, 6

Terminology Distinction

• "Fetal growth restriction (FGR)" refers to prenatal ultrasound diagnosis of EFW <10th percentile 1, 2
• "Small for gestational age (SGA)" should be reserved exclusively for newborns with birth weight <10th percentile 1, 2
• The outdated term "intrauterine growth restriction (IUGR)" should be abandoned in favor of FGR for prenatal diagnosis 1

When to Suspect Abnormal Growth

At 35 weeks gestation, further evaluation with umbilical artery Doppler is warranted if:

• EFW falls below the 10th percentile to differentiate pathological restriction from constitutional smallness 1, 6
• Fundal height measures ≥3 cm below expected gestational age 6
• Oligohydramnios is present (maximum vertical pocket <2 cm or amniotic fluid index <5 cm) 6
• Maternal risk factors exist, including chronic hypertension, preeclampsia, prior FGR, or antiphospholipid syndrome 6