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Pregnancy Due Date Formula:
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The pregnancy due date calculation estimates the expected delivery date based on the first day of the last menstrual period (LMP). This method, known as Naegele's rule, adds 280 days (40 weeks) to the LMP to determine the estimated due 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 calculation is essential for proper prenatal care, 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 provide your estimated due date, current gestational age, and days remaining until delivery. For best accuracy, use the exact date from your medical records.
Q1: How accurate is the due date calculation?
A: The due date is an estimate - only about 5% of women deliver on their exact due date. Most deliveries occur within 2 weeks before or after the calculated date.
Q2: What if I have irregular periods?
A: For women with irregular cycles, an early ultrasound (first trimester) provides a more accurate due date than LMP-based calculation.
Q3: Why 280 days instead of 9 months?
A: Pregnancy is calculated as 40 weeks from LMP, which equals 280 days. This accounts for the fact that conception typically occurs about 2 weeks after the LMP.
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 difference from the LMP-based calculation.
Q5: What are the trimesters of pregnancy?
A: First trimester: weeks 1-13, Second trimester: weeks 14-27, Third trimester: weeks 28-40. Each trimester has specific developmental milestones and care requirements.