What is a dating scan
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.
Having a scan in the first few months of pregnancy can be a thrilling experience.
It's amazing to see the little blob with a heartbeat that will soon become your baby.
You'll be given a report of the scan which will tell you exactly how many weeks pregnant you are.
Keep it with your maternity notes so your midwife and anyone else involved in your care can see it. This measurement, known as the crown rump length (CRL), is very accurate in the first trimester.
This is because blood tests for Down syndrome are not very accurate if you are having more than one baby.