Calcular Peso Fetal

Estimating fetal weight is an important part of prenatal care. Our calculator provides accurate estimates based on ultrasound measurements and gestational age. This guide explains how to use the calculator, understand the results, and what they mean for your pregnancy.

How to Use This Calculator

To estimate your baby's weight, you'll need two key pieces of information from your ultrasound:

Gestational age (in weeks)
Biparietal diameter (BPD) measurement in millimeters

Enter these values into the calculator and click "Calculate". The calculator will provide an estimated fetal weight in grams and ounces.

Note: These calculations are estimates only. Actual fetal weight may vary. Always consult with your healthcare provider for personalized advice.

Fetal Weight Estimation Methods

The calculator uses two common methods for fetal weight estimation:

Hadlock Formula

This formula is based on the relationship between fetal weight and biparietal diameter (BPD):

Weight (grams) = 1.28 × (BPD in cm)³ - 3.29 × (BPD in cm)² + 87.5 × (BPD in cm) - 59.3

Where BPD is measured in centimeters.

Hadlock II Formula

An updated version that includes gestational age:

Weight (grams) = 1.28 × (BPD in cm)³ - 3.29 × (BPD in cm)² + 87.5 × (BPD in cm) - 59.3 + 128 × (GA in weeks - 22)

This formula provides a more accurate estimate by incorporating both ultrasound measurements and gestational age.

Interpreting Your Results

Fetal weight estimates help monitor growth and identify potential issues. Here's what your results might indicate:

Normal Weight Range

For a healthy pregnancy, fetal weight typically falls within the 10th to 90th percentile of the growth chart. If your baby's estimated weight is outside this range, it may warrant further investigation.

Example Calculation

Let's say you're 32 weeks pregnant with a BPD measurement of 5.2 cm:

Using Hadlock formula: 1.28 × (5.2)³ - 3.29 × (5.2)² + 87.5 × (5.2) - 59.3 ≈ 2,800 grams (6.17 lbs)
Using Hadlock II formula: 2,800 + 128 × (32 - 22) ≈ 3,200 grams (7.05 lbs)

This would be considered a normal weight for a term baby.

Remember: These are estimates only. Actual birth weight may vary by several hundred grams. Always consult with your healthcare provider for personalized advice.

Frequently Asked Questions

How accurate are fetal weight estimates?

Fetal weight estimates are generally accurate within about 10% of the actual birth weight. However, individual variations can occur, especially in early or late pregnancies.

When should I be concerned about fetal growth?

Consult your healthcare provider if your baby's estimated weight is consistently below the 10th percentile or above the 90th percentile for several weeks. Other symptoms like reduced movement or abnormal growth patterns may also indicate issues.

Can I use this calculator for multiple pregnancies?

This calculator is designed for singleton pregnancies. For multiple pregnancies, specialized formulas and additional measurements are typically required.

How often should I check my baby's weight?

Your healthcare provider will recommend a schedule based on your pregnancy. Typically, weight is monitored at each ultrasound appointment, which is usually every 4 weeks.