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NHS Due Date Calculation:
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The NHS Due Date Pregnancy Calculator estimates the expected delivery date based on the first day of your last menstrual period (LMP), following the standard NHS calculation method of adding 280 days (40 weeks).
The calculator uses the standard NHS due date formula:
Where:
Explanation: This calculation is based on the assumption of a regular 28-day menstrual cycle and ovulation occurring on day 14. The due date represents the estimated date of delivery (EDD).
Details: Accurate due date calculation is essential for proper prenatal care scheduling, fetal development monitoring, and planning for delivery. It helps healthcare providers track pregnancy progress and identify any potential complications.
Tips: Enter the first day of your last menstrual period in the date field. Ensure the date is accurate for the most reliable due date estimation. The calculator will provide your estimated due date based on NHS standards.
Q1: How accurate is the due date calculation?
A: The due date is an estimate - only about 5% of babies are born on their exact due date. Most births occur within two weeks before or after the estimated date.
Q2: What if I have irregular periods?
A: If you have irregular periods, an early ultrasound scan (dating scan) between 8-14 weeks provides a more accurate due date estimation.
Q3: Can the due date change during pregnancy?
A: Yes, healthcare providers may adjust the due date based on early ultrasound measurements if there's a significant difference from the LMP-based calculation.
Q4: Why 280 days specifically?
A: 280 days represents 40 weeks of pregnancy, calculated from the first day of the last menstrual period rather than conception date.
Q5: When should I contact my midwife or doctor?
A: Contact your healthcare provider as soon as you suspect you're pregnant to begin proper prenatal care and confirm your due date.