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Pregnancy Calculation Formula:
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The Pregnancy Calculator based on Last Menstrual Period estimates the due date and current gestational age using the first day of the woman's last menstrual period. This is the most common method used in clinical practice for pregnancy dating.
The calculator uses the standard pregnancy calculation formula:
Where:
Explanation: This calculation assumes a regular 28-day menstrual cycle with ovulation occurring on day 14. The 280 days represents 40 weeks of gestation.
Details: Accurate pregnancy dating is crucial for proper prenatal care, monitoring fetal development, scheduling important tests, and determining the optimal time for delivery.
Tips: Enter the first day of your last menstrual period in the date field. The calculator will provide your estimated due date and current gestational age. Ensure the date entered is accurate for best results.
Q1: How accurate is the LMP-based due date calculation?
A: LMP dating is accurate for women with regular cycles. For irregular cycles, ultrasound dating in early pregnancy is more reliable.
Q2: What if I don't remember my last menstrual period?
A: If you're unsure of your LMP, an early pregnancy ultrasound (6-12 weeks) can provide accurate dating based on fetal measurements.
Q3: Why 280 days instead of 9 months?
A: Pregnancy is calculated as 40 weeks (280 days) from LMP, which is approximately 9 calendar months plus one week.
Q4: Can my due date change during pregnancy?
A: Yes, if early ultrasound measurements differ significantly from LMP-based dating, healthcare providers may adjust the due date.
Q5: What percentage of babies are born on their due date?
A: Only about 5% of babies are born exactly on their due date. Most are born within two weeks before or after the estimated date.