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Gestational Age Formula:
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Crown Rump Length (CRL) dating is a method used in early pregnancy to estimate gestational age by measuring the length of the embryo or fetus from the top of the head (crown) to the bottom of the buttocks (rump). This measurement provides the most accurate estimation of gestational age during the first trimester.
The calculator uses the gestational age formula:
Where:
Explanation: This formula calculates gestational age based on the square root of the crown rump length measurement, providing an accurate estimation of fetal age in early pregnancy.
Details: Accurate gestational age determination is crucial for proper pregnancy dating, monitoring fetal development, scheduling appropriate prenatal tests, and establishing accurate expected delivery dates.
Tips: Enter the crown rump length measurement in centimeters. The value must be greater than zero. The calculator will provide the gestational age in days.
Q1: When is CRL measurement most accurate?
A: CRL measurement is most accurate between 6-13 weeks of gestation. After 13 weeks, other measurements like biparietal diameter become more reliable.
Q2: How is CRL measured?
A: CRL is measured via ultrasound in a sagittal plane with the embryo/fetus in a neutral position, from the top of the head to the bottom of the rump.
Q3: What is the typical CRL range?
A: CRL typically ranges from about 0.3 cm at 6 weeks to 7.4 cm at 13 weeks gestation.
Q4: Are there limitations to CRL dating?
A: Accuracy decreases with advancing gestation, and measurements may be affected by fetal position, maternal factors, and ultrasound equipment quality.
Q5: How does CRL dating compare to LMP dating?
A: CRL dating is generally more accurate than last menstrual period (LMP) dating, especially when menstrual cycles are irregular or LMP date is uncertain.