Question 1

What is the Estimated Due Date (EDD)?

Accepted Answer

The Estimated Due Date (EDD) is the predicted date your baby will be born, calculated at 40 weeks (280 days) from the first day of your last menstrual period. It is the standard obstetric term used in clinical records worldwide.

Question 2

How is the EDD calculated using Naegele's Rule?

Accepted Answer

Naegele's Rule adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). Practically: take your LMP date, add 1 year, subtract 3 months, and add 7 days. For example, if your LMP was January 1st, your EDD would be around October 8th of the same year.

Question 3

How accurate is the EDD at predicting the actual birth date?

Accepted Answer

The EDD is a statistical estimate: only 4–5% of babies are born exactly on their due date. About 90% of births happen between weeks 37 and 42. The EDD is often revised after the first-trimester ultrasound (weeks 10–13), which is more accurate.

Question 4

Can my EDD change during pregnancy?

Accepted Answer

Yes. If the first-trimester ultrasound measurement differs by more than 7 days from the calculated EDD, your doctor will update the official due date. Ultrasound-based dating in the first trimester is the most accurate method available.

Question 5

What if my menstrual cycle is not 28 days?

Accepted Answer

Standard Naegele's Rule assumes a 28-day cycle. If your cycle is longer (e.g., 35 days), your EDD shifts forward; if shorter (e.g., 21 days), it shifts back. Our calculator lets you adjust your cycle length for a more accurate estimate.

Question 6

Does the EDD differ for IVF pregnancies?

Accepted Answer

Yes. For IVF pregnancies, the EDD is calculated from the embryo transfer date plus the days of embryo development (typically 3 or 5 days). This provides a more precise date than the last menstrual period method.

Calculadora de Data do Parto