1. What is the Estimated Birth Weight Formula?

The Estimated Birth Weight formula calculates fetal weight using ultrasound measurements of abdominal circumference, biparietal diameter, and femur length multiplied by a correction factor. This method provides a non-invasive way to estimate fetal weight during pregnancy.

2. How Does the Calculator Work?

The calculator uses the following equation:

Where:

• Abdominal circumference — Measured in centimeters (cm)
• Biparietal diameter — Measured in centimeters (cm)
• Femur length — Measured in centimeters (cm)
• Factor — Correction factor (typically 0.061)

Explanation: The formula multiplies three key fetal measurements with a correction factor to estimate weight in grams.

3. Importance of Birth Weight Estimation

Details: Accurate fetal weight estimation helps identify growth abnormalities (IUGR or macrosomia), guides delivery planning, and assesses fetal well-being.

4. Using the Calculator

Tips: Enter all measurements in centimeters. The default factor is 0.061 but may be adjusted based on population-specific studies. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: How accurate is this estimation method?
A: This method has an accuracy of ±15% of actual birth weight when measurements are taken close to delivery.

Q2: What is the typical factor value?
A: The most commonly used factor is 0.061, but some studies suggest 0.066 may be more accurate in certain populations.

Q3: When should fetal weight be estimated?
A: Typically performed in third trimester, especially when growth abnormalities are suspected or for delivery planning.

Q4: What are limitations of this method?
A: Accuracy decreases with extreme fetal weights, maternal obesity, and oligohydramnios.

Q5: Are there alternative formulas?
A: Yes, other formulas like Hadlock's use different combinations of measurements and may be more accurate in specific cases.