The scan or my dates - which should I believe? 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.

How does an ultrasound date a pregnancy?

An ultrasound is actually the most accurate way to date a pregnancy because all fetuses grow at a consistent rate during the first trimester and early second. In other words, if your baby measures 9 weeks 2 days when you have your ultrasound, thats how far along you are, no matter when your last period was.

How does the scan count pregnancy?

The point of the scan is to work out how many weeks pregnant you are. You may have calculated the length of your pregnancy from the first day of your last menstrual period (LMP). However, conception doesnt actually occur until around 14 days after your LMP, or later if your cycle is longer than 28 days.

Can you find out the father of the baby while pregnant?

A DNA paternity test is nearly 100% accurate at determining whether a man is another persons biological father. DNA tests can use cheek swabs or blood tests. You must have the test done in a medical setting if you need results for legal reasons. Prenatal paternity tests can determine fatherhood during pregnancy.