Fetal Weight Estimator
By Gestational Week
Estimate fetal weight based on current gestational week
By Ultrasound Measurements
Estimate weight using biparietal diameter and abdominal circumference
Formula
Hadlock formula: log10(EFW) = 1.1134 + 0.05845*AC - 0.000604*AC^2 - 0.007365*BPD^2 + 0.000595*BPD*AC + 0.1694*BPD (measurements in cm, weight in grams).
Frequently Asked Questions
How accurate are fetal weight estimates?
Ultrasound fetal weight estimates have a margin of error of about ±10-15%. The accuracy depends on the gestational age, baby's position, and the measurements used. Multiple measurement formulas (like Hadlock) improve accuracy.
What is a normal fetal weight?
Normal fetal weight varies by gestational age. At 20 weeks, average is about 300g (10.6 oz). At 30 weeks, about 1,300g (2.9 lbs). At 40 weeks (full term), average birth weight is about 3,400g (7.5 lbs). The normal range is quite wide.
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