It may also be offered after 11 or 12 weeks if a trans-abdominal scan doesn’t give a clear enough picture.
A scan can help doctors to see whether the pregnancy is inside or outside your womb (uterus), but can't tell much else before six weeks.
If you just want a scan for reassurance that you are having a healthy pregnancy, do try to wait a bit longer.
If you do know the conception date, this is counted as day 14, not day one.
If your cycle is irregular or you've recently been on the pill, working out the date from your LMP probably won't work. If the scan date differs from your period dates, the scan date will be used.
Most dating scans are done with a trans-abdominal transducer and a fullish bladder.
If the pregnancy is very early the gestation sac and fetus will not be big enough to see, so the transvaginal approach will give better pictures.
If so, you'll have these scans in early pregnancy at clinics in larger hospitals.
Even if you've had a miscarriage before, as long as your current pregnancy is going well, you may not be offered a scan. So if you need the reassurance, your GP should be able to request an early scan for you.
The scan will usually show that your pregnancy is less far along than suggested by your LMP.
This means that accurate dating reduces your chance of having your labour induced because your baby is thought to be overdue.
The only reason for having a scan before you’re six weeks pregnant is to rule out an ectopic pregnancy.