If you have an irregular cycle, or if you've recently been taking the contraceptive pill, working out the date from your LMP isn't a very accurate method. The scan can check that your baby has a heartbeat and is developing normally.Your baby's head, limbs, hands and feet, and some organs can be seen.Without an accurate due date, a blood test at what you thought was 13 weeks wouldn't be helpful if you were 16 weeks pregnant when the blood was taken. National Down's Syndrome Screening Programme for England.
Ask your GP if you want the reassurance of an early scan. The scan's main purpose is to work out accurately how many weeks pregnant you are and estimate your due date.This measures a collection of fluid under the skin at the back of a baby's neck.The dating scan will take between five minutes and 10 minutes.Finding out about having twins early in pregnancy also gives you more time to prepare for the birth and for your doctor or midwife to plan your care.Knowing about twins early is also useful if you want to have screening for Down syndrome.