If you have more than one ultrasound during your pregnancy, giving you 'multiple dates', then the earliest ultrasound estimate should be used, because it will be more accurate.If you have any questions about this, please feel free to talk to your sonographer or doctor about it.
This is presuming that the pregnancy is actually at this stage of development.
Sometimes a trans-vaginal examination shows that your pregnancy is less advanced than expected.
The due date is referred to as the estimated date of confinement (EDC).
This is a throwback to the days when a woman was “confined” to bed and home for a period of time after birth until convalescence was complete.
Usually the expected date of delivery (EDD or EDC) is calculated from your last menstrual period - if the early dating scan calculates the EDD to be within 5 days of the EDD from your last menstrual period.
The EDD from the early dating scan is used - if the last menstrual period is not known or is unreliable, or the dating scan differs from the last menstrual period dating by more than 5 days.But since no one is pregnant before conception, this is a source of confusion on every pregnancy until the way we count is explained. Divided into perfect four-week months, this comes out to ten perfect months.But Julius Caesar and Pope Gregory XIII, the architects of the modern calendar, were thinking of anything but gestation when, as the sing-song goes, “Thirty days hath September, April, June, and November.” (It goes without saying that all the rest but one have thirty-one….) If an obstetrician had designed the calendar, every month would have 28 days (“and no more”), comprising 13 perfect four-week months per year.It was a term contemporary with the “lying-in” that meant the same thing.By the time you’re “late” for your period, that period which will never come, you are already two weeks past the time of conception.According to the usual way pregnancy is calculated, you are considered four weeks pregnant.