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Pregnancy Calculator Formula:
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The Pregnancy Calculator Lister estimates the due date (EDD) based on the last menstrual period (LMP) using the standard formula of adding 280 days. This method, also known as Naegele's rule, is widely used in obstetrics for pregnancy dating.
The calculator uses the standard pregnancy dating formula:
Where:
Explanation: This calculation assumes a regular 28-day menstrual cycle and ovulation occurring on day 14. The 280 days represent 40 weeks of gestation.
Details: Accurate due date estimation is crucial for monitoring fetal development, scheduling prenatal care, determining gestational age, and planning for delivery. It helps healthcare providers track pregnancy progress and identify potential complications.
Tips: Enter the first day of your last menstrual period in the date field. Ensure the date is accurate for the most reliable due date estimation. The calculator will automatically compute your estimated due date.
Q1: How accurate is this due date calculation?
A: This method provides a good estimate, but only about 5% of women deliver on their exact due date. Most deliveries occur within 2 weeks before or after the estimated date.
Q2: What if my menstrual cycle is irregular?
A: For women with irregular cycles, this calculation may be less accurate. An early ultrasound (first trimester) provides more reliable dating.
Q3: Why 280 days instead of 9 months?
A: Pregnancy is calculated as 40 weeks from LMP, which equals 280 days. This differs from calendar months due to varying month lengths.
Q4: Can the due date change during pregnancy?
A: Yes, healthcare providers may adjust the due date based on ultrasound measurements, especially if there's a significant discrepancy from LMP-based calculation.
Q5: What other methods are used to calculate due dates?
A: Ultrasound dating (especially first-trimester crown-rump length), conception date, and IVF transfer dates can also be used for more accurate dating.