Normal Fetal Weight at 29 Weeks Gestation
At 29 weeks gestation, the normal estimated fetal weight for a healthy singleton pregnancy typically ranges from approximately 1,100 to 1,400 grams (mean approximately 1,200-1,250 grams), based on population-based growth standards such as the Hadlock curves. 1, 2
Understanding Fetal Weight Assessment at 29 Weeks
Standard Measurement Approach
- Estimated fetal weight (EFW) at 29 weeks is calculated using ultrasound biometric measurements including biparietal diameter, head circumference, abdominal circumference, and femur length through regression equations 1, 2
- The Hadlock formula remains the most accurate method for estimating fetal weight in preterm populations, with a mean percentage error of -0.7% (SD 10.1) compared to actual birth weight when delivery occurs near the time of measurement 3
Normal Weight Range Definition
- Population-based fetal growth references (Hadlock curves) should be used to determine fetal weight percentiles at 29 weeks 1, 2
- A fetus is considered appropriate for gestational age when the EFW falls between the 10th and 90th percentiles for 29 weeks 1, 2, 4
- Weight below the 10th percentile at 29 weeks defines fetal growth restriction (FGR), while weight above the 90th percentile defines large-for-gestational-age (LGA) 1, 2, 4
Clinical Context at 29 Weeks
Early-Onset Growth Concerns
- At 29 weeks, any detected growth abnormality would be classified as early-onset (diagnosed before 32 weeks), which typically indicates more severe placental pathology and carries higher risk 2
- If FGR is suspected at 29 weeks with EFW below the 3rd percentile, this represents severe FGR with increased risk of adverse perinatal outcomes regardless of Doppler findings 1, 2
Measurement Accuracy Considerations
- Ultrasound estimation of fetal weight has inherent limitations, with approximately 68-75% of estimates falling within ±10% of actual birth weight 3, 5
- The Hadlock formula demonstrates superior accuracy at gestational ages around 29 weeks compared to alternative formulas like INTERGROWTH, particularly in the 29-31 week range where mean error is only -0.6% 3
Common Clinical Pitfalls
- Avoid using customized growth charts alone: While customized standards may detect LGA with higher sensitivity, population-based standards (Hadlock) are recommended for consistency and are the guideline-endorsed approach 1, 2, 4
- Do not rely on single measurements: Serial growth assessments are more valuable than isolated weight estimates, as growth velocity provides additional prognostic information 6
- Accurate dating is essential: First-trimester crown-rump length measurement must be used to establish accurate gestational age before interpreting fetal weight percentiles at 29 weeks 1, 2