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Perinatology Formula:
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The Crown Rump Length Calculator estimates gestational age using the perinatology formula based on the measurement of the embryo or fetus from the top of the head (crown) to the bottom of the buttocks (rump). This measurement is typically obtained during early pregnancy ultrasound examinations.
The calculator uses the perinatology formula:
Where:
Explanation: This formula provides an accurate estimation of gestational age during the first trimester of pregnancy, typically between 6-13 weeks gestation.
Details: Accurate gestational age determination is crucial for proper prenatal care, timing of screenings and tests, monitoring fetal development, and establishing an accurate due date.
Tips: Enter the crown rump length measurement in centimeters as obtained from an ultrasound examination. The value must be greater than zero.
Q1: How accurate is CRL for dating pregnancy?
A: CRL measurement is the most accurate method for dating early pregnancy, with an accuracy of ±5-7 days when measured between 6-13 weeks gestation.
Q2: When is CRL measurement most reliable?
A: CRL is most reliable between 7-12 weeks gestation. After 13 weeks, other biometric measurements (such as biparietal diameter) become more accurate for dating.
Q3: What factors can affect CRL measurement accuracy?
A: Fetal position, ultrasound equipment quality, technician experience, and fetal curvature can all impact measurement accuracy.
Q4: How is CRL different from other pregnancy dating methods?
A: CRL provides more accurate dating in early pregnancy compared to last menstrual period dating, which can be affected by irregular cycles or recall error.
Q5: Can this formula be used throughout pregnancy?
A: No, this specific formula is designed for first trimester dating only. Different formulas are used for dating pregnancy in the second and third trimesters.