1. What is the Due Date Calculation?

The due date calculation estimates the most likely delivery date based on the last menstrual period (LMP). The standard calculation adds 280 days (40 weeks) to the first day of the LMP, with a typical range of ±7 days.

2. How Does the Calculator Work?

The calculator uses the standard obstetric formula:

Where:

• LMP — First day of last menstrual period
• 280 days — Standard length of human gestation
• ±7 days — Typical range for normal delivery

Explanation: This calculation (Naegele's rule) assumes a regular 28-day menstrual cycle with ovulation on day 14. Actual delivery dates vary naturally.

3. Importance of Due Date Estimation

Details: Accurate due date estimation is crucial for prenatal care scheduling, monitoring fetal development, and determining post-term pregnancies.

4. Using the Calculator

Tips: Enter the first day of your last menstrual period. The calculator will show the estimated due date and the most likely delivery window.

5. Frequently Asked Questions (FAQ)

Q1: How accurate is this calculation?
A: Only about 5% of women deliver on their exact due date, but most deliver within 2 weeks before or after.

Q2: What if my cycle isn't 28 days?
A: For irregular cycles or known ovulation dates, ultrasound dating in early pregnancy is more accurate.

Q3: When should I get an ultrasound confirmation?
A: First trimester ultrasounds (8-13 weeks) provide the most accurate dating, with ±5-7 day accuracy.

Q4: Can the due date change?
A: Yes, early ultrasound may adjust the due date if there's significant discrepancy with LMP-based dating.

Q5: What's considered full term?
A: 39-40 weeks is full term. 37-38 weeks is early term, and 41+ weeks is late term.