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.

How accurate is the dating scan?

The earlier the ultrasound is done, the more accurate it is at estimating the babys due date. Ultrasounds performed during the first 12 weeks of pregnancy are generally within 3 - 5 days of accuracy. The most accurate time is between 8 and 11 weeks gestation.

How do sonographers determine due date?

How is a due date estimated?counting 280 days from the first day of your last monthly period.estimating your babys size from various measurements made during an ultrasound scan.Feb 28, 2020

What a baby looks like at 7 weeks?

By 7 weeks, the embryo has grown to about 10mm long from head to bottom. This measurement is called the crown-rump length. The brain is growing rapidly and this results in the head growing faster than the rest of the body. The embryo has a large forehead, and the eyes and ears continue to develop.