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Perinatal Due Date Formula:
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The perinatal due date calculation estimates the expected delivery date based on the first day of the last menstrual period. This method, known as Naegele's rule, is widely used in obstetrics to determine the estimated due date (EDD).
The calculator uses the standard obstetric formula:
Where:
Explanation: This calculation assumes a regular 28-day menstrual cycle and adds 280 days (40 weeks) to the first day of the last menstrual period to estimate the delivery date.
Details: Accurate due date estimation is crucial for prenatal care planning, monitoring fetal development, scheduling important tests, and preparing 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. The calculator will automatically compute and display both your LMP and estimated due date. Ensure you enter the correct first day of your last period for accurate results.
Q1: How accurate is the 280-day calculation?
A: While 280 days is the standard, only about 5% of women deliver exactly on their due date. Most deliveries occur within two weeks before or after the estimated date.
Q2: What if my menstrual cycle is irregular?
A: For women with irregular cycles, an early ultrasound (first trimester) provides a more accurate due date estimation than LMP-based calculation alone.
Q3: Why is the calculation based on LMP rather than conception date?
A: LMP is typically more reliably known than conception date, and it establishes a standardized reference point for pregnancy dating across healthcare providers.
Q4: Can the due date change during pregnancy?
A: Yes, healthcare providers may adjust the due date based on early ultrasound measurements, especially if there's a significant discrepancy with LMP-based calculation.
Q5: What are the trimesters based on this calculation?
A: First trimester: weeks 1-13, Second trimester: weeks 14-27, Third trimester: weeks 28-40+.