The ultrasound can detect the fetuss heartbeat around the 6th week, and this is one of the ways your health care provider can tell how far along you are in your pregnancy. The first ultrasound, done between 10 and 14 weeks, is considered the most accurate method of estimating when you conceived.

When did I conceive calculator based on due date?

In cases where the date of conception is known precisely, such as with in vitro fertilization, the EDD is calculated by adding 266 days to the date of conception. Ultrasound uses the size of the fetus to determine the gestational age (the time elapsed since the the first day of the last menstrual period).

How many weeks pregnant am I based on conception date?

First day of last period Most pregnancies last around 40 weeks (or 38 weeks from conception), so typically the best way to estimate your due date is to count 40 weeks, or 280 days, from the first day of your last menstrual period (LMP).

How accurate is due date based on conception?

A recent study3 of women who conceived by IVF and therefore knew when their egg was fertilised, found that the routine ultrasound dating scan consistently put their estimated birth date earlier than it should have been by an average of 3 days.