1. What is Gestational Age?

Gestational age is the common term used during pregnancy to describe how far along the pregnancy is. It is measured in weeks from the first day of the woman's last menstrual period to the current date.

2. How Ultrasound Measurements Estimate Gestational Age

Ultrasound measurements of fetal anatomy correlate with gestational age. The calculator uses standard formulas for:

• Biparietal Diameter (BPD): Diameter between the two parietal bones of the fetal head
• Head Circumference (HC): Circumference of the fetal head
• Abdominal Circumference (AC): Circumference of the fetal abdomen
• Femur Length (FL): Length of the fetal thigh bone

Note: Accuracy is best in first trimester (±5-7 days) and decreases as pregnancy progresses.

3. Importance of Accurate Gestational Age

Details: Accurate dating is crucial for proper prenatal care, timing of tests, evaluating fetal growth, and determining delivery timing.

4. Using the Calculator

Tips: Select the measurement type and enter the value in millimeters. The most accurate estimates come from first trimester measurements.

5. Frequently Asked Questions (FAQ)

Q1: Which measurement is most accurate?
A: In first trimester, crown-rump length is most accurate. Later, combining multiple measurements improves accuracy.

Q2: How does this compare to LMP dating?
A: Ultrasound dating is more accurate, especially if LMP is uncertain or cycles are irregular.

Q3: When should ultrasound dating be used?
A: Recommended for all pregnancies, especially when there's >5 days discrepancy between LMP and ultrasound dating in first trimester.

Q4: Are there limitations to ultrasound dating?
A: Accuracy decreases with advancing gestation. Abnormal fetal growth may affect measurements.

Q5: How often should gestational age be confirmed?
A: Typically established at first ultrasound and not changed unless significant discrepancy is found early in pregnancy.