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EDD Calculation Formula:
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The Pregnancy Calculator based on Last Period estimates the due date (EDD) by adding 280 days (40 weeks) to the first day of the last menstrual period. This is the most common method used to calculate pregnancy due dates.
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 280 days represents 40 weeks of gestation.
Details: Accurate due date calculation is crucial for monitoring fetal development, scheduling prenatal care, determining gestational age, and planning for delivery. It helps healthcare providers track pregnancy milestones and identify potential complications.
Tips: Enter the first day of your last menstrual period in the date field. Ensure the date is accurate as this forms the basis for all subsequent pregnancy dating. The calculator will provide both the estimated due date and current weeks of pregnancy.
Q1: How accurate is the last period method?
A: It's reasonably accurate for women with regular 28-day cycles. For irregular cycles, ultrasound dating in early pregnancy may be more precise.
Q2: What if I don't remember my last period date?
A: An early pregnancy ultrasound (before 14 weeks) can provide an accurate due date based on fetal measurements.
Q3: Why 280 days instead of 9 months?
A: Pregnancy is calculated in weeks (40 weeks) rather than calendar months because months have varying lengths. 280 days equals 40 weeks.
Q4: Can the due date change?
A: Yes, healthcare providers may adjust the due date based on early ultrasound findings or if menstrual dates are uncertain.
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 are born within two weeks before or after the calculated date.