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Pregnancy Due Date Formula:
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The Pregnancy Due Date Calculator estimates your expected delivery date based on your last menstrual period using the standard Naegele's rule. This calculation provides an approximate date around which you can expect to deliver your baby.
The calculator uses the standard pregnancy 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 pregnancy.
Details: Knowing your estimated due date helps in planning prenatal care, monitoring fetal development, preparing for delivery, and ensuring both maternal and fetal wellbeing throughout the pregnancy journey.
Tips: Enter the first day of your last menstrual period accurately. The calculator will provide your estimated due date, current pregnancy duration in weeks and days, and total days since your LMP.
Q1: How accurate is this due date calculation?
A: This method is about 60-70% accurate. Only about 5% of babies are born exactly on their due date, with most deliveries occurring within 2 weeks before or after.
Q2: What if my menstrual cycle is irregular?
A: For irregular cycles, an early ultrasound (usually between 8-12 weeks) provides a more accurate due date estimation.
Q3: Why 280 days/40 weeks?
A: Pregnancy is calculated from the first day of your last period, which is typically about 2 weeks before conception actually occurs, making total gestation approximately 38 weeks from conception.
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 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 distinct developmental milestones.