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EDD Calculation Formula:
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The What To Expect Baby Calculator estimates your due date (EDD) based on your last menstrual period (LMP). This calculation follows the standard obstetric practice of adding 280 days (40 weeks) to the first day of your last menstrual period.
The calculator uses the standard EDD formula:
Where:
Explanation: This calculation assumes a regular 28-day menstrual cycle and ovulation occurring on day 14. The calculator also shows your current pregnancy progress in weeks and days.
Details: Knowing your estimated due date is crucial for proper prenatal care, monitoring fetal development, planning for delivery, and ensuring both mother and baby receive appropriate medical attention throughout the pregnancy.
Tips: Enter the first day of your last menstrual period in the date field. Make sure to use the correct date format and ensure the date is accurate for the most reliable due date estimation.
Q1: How accurate is this due date calculation?
A: This method is about 70% accurate for predicting delivery within ±7 days of the estimated date, and 90% accurate within ±14 days.
Q2: What if my menstrual cycle is irregular?
A: For irregular cycles, an ultrasound dating scan in the first trimester provides a more accurate due date estimation.
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 my due date change?
A: Yes, healthcare providers may adjust your due date based on ultrasound measurements, especially if there's a significant difference from LMP-based calculation.
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 births occur between 37-42 weeks of pregnancy.