1. What Is Ultrasound Gestational Age?

Ultrasound gestational age is the estimated age of pregnancy calculated from ultrasound measurements of the fetus. It provides a more accurate assessment of fetal development than menstrual dating alone, especially when the last menstrual period is uncertain.

2. How Ultrasound Weeks Are Calculated

The calculator uses standard fetal biometry formulas:

Common measurement types:

• Crown-Rump Length (CRL) - Most accurate in first trimester
• Biparietal Diameter (BPD) - Head measurement
• Femur Length (FL) - Long bone measurement
• Abdominal Circumference (AC) - Abdominal size

Explanation: Each measurement type has specific regression equations that convert millimeter measurements to gestational age in weeks.

3. Importance of Accurate Dating

Details: Accurate gestational dating is crucial for monitoring fetal growth, scheduling prenatal tests, determining viability, and managing high-risk pregnancies. It helps identify growth restrictions or accelerations.

4. Using the Calculator

Tips: Enter ultrasound weeks, select measurement type, input measurement value in millimeters, and provide last menstrual period date. The calculator will determine gestational age and estimated due date.

5. Frequently Asked Questions (FAQ)

Q1: Which measurement is most accurate?
A: Crown-rump length in first trimester (±3-5 days), biparietal diameter in second trimester (±7-10 days).

Q2: Why might ultrasound dating differ from LMP?
A: Irregular cycles, late ovulation, or inaccurate LMP recall can cause discrepancies.

Q3: When is ultrasound dating most reliable?
A: First trimester (7-13 weeks) provides the most accurate dating.

Q4: Can ultrasound dating change later in pregnancy?
A: Dating is usually established in first trimester and not changed later unless significant discrepancies exist.

Q5: What if measurements don't match gestational age?
A: Discrepancies may indicate growth issues requiring further evaluation.