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Gestational Age Formula:
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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 (LMP) to the current date.
The calculator uses the standard obstetrical formula:
Where:
Explanation: This calculation follows the standard obstetrical practice of calculating gestational age from the LMP, which assumes conception occurred approximately 2 weeks after the LMP.
Details: Accurate gestational age determination is crucial for proper prenatal care, scheduling of tests, determining due date, and assessing fetal growth and development.
Tips: Enter the first day of the last menstrual period and the current date (or any date you want to calculate gestational age for). The calculator will display the gestational age in weeks and days.
Q1: What if I don't know my LMP?
A: If LMP is unknown, an ultrasound measurement in early pregnancy (especially first trimester) can provide an accurate estimate of gestational age.
Q2: How accurate is this method?
A: This method is accurate for women with regular 28-day cycles who conceived at approximately day 14. Variations occur with irregular cycles or conception at different times.
Q3: What's the difference between gestational age and fetal age?
A: Gestational age is about 2 weeks more than fetal age (conception age), as it counts from LMP rather than actual conception date.
Q4: When should I use ultrasound dating instead?
A: Ultrasound dating should be used when LMP is unknown, cycles are irregular (>35 days), or when there's significant discrepancy between LMP and ultrasound dating.
Q5: How is this different from Naegele's rule?
A: Naegele's rule calculates the due date (LMP + 1 year - 3 months + 7 days), while this calculator shows current gestational age.