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Pregnancy Due Date Formula:
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The Pregnancy Due Date Calculator estimates the expected delivery date (EDD) based on the first day of the last menstrual period (LMP). This calculation uses Naegele's rule, which adds 280 days (40 weeks) to the LMP date.
The calculator uses the standard obstetric formula:
Where:
Explanation: This calculation assumes a regular 28-day menstrual cycle and ovulation occurring on day 14. The due date represents the end of 40 weeks of gestation.
Details: Accurate due date estimation is crucial for proper prenatal care, monitoring fetal development, scheduling important tests, and preparing for delivery. It helps healthcare providers track pregnancy progress and identify any potential complications.
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. For women with irregular cycles or uncertain LMP dates, ultrasound dating may be more accurate.
Q1: How Accurate Is The LMP Method?
A: The LMP method is reasonably accurate for women with regular 28-day cycles. However, only about 5% of babies are born exactly on their due date - most deliver within two weeks before or after.
Q2: What If My Cycle Isn't 28 Days?
A: For cycles longer or shorter than 28 days, adjust the calculation: EDD = LMP + 280 days + (actual cycle length - 28 days).
Q3: How Is Gestational Age Different From Fetal Age?
A: Gestational age is calculated from the LMP (about 2 weeks before conception), while fetal age (conceptual age) starts at conception. A 40-week pregnancy represents 38 weeks of fetal development.
Q4: When Should I Confirm With Ultrasound?
A: Early ultrasound (8-13 weeks) provides the most accurate dating. Later ultrasounds are less reliable for establishing due dates.
Q5: Can The Due Date Change?
A: Yes, healthcare providers may adjust the due date based on early ultrasound measurements, especially if there's a significant difference from the LMP-based calculation.