In the first trimester, your baby is measured from head to bottom. The CRL is very accurate in the first trimester, but after 13 weeks your baby can curl up and stretch out, so measuring the length becomes more difficult.
However, if the doctor needs to check your cervix (mouth of uterus and birth canal), a transvaginal scan may be done as it is more accurate.
It's a good idea to wear loose or two-piece clothing such as a salwar kameez or a top and comfortable pants so you won't need to get fully undressed.
Experts recommend having your first scan when you are six weeks pregnant. At six weeks, the scan is done to: Your next scan is likely to be the nuchal translucency scan between 11 and 13 weeks. It is possible that you might miss your first scan if you do not meet your doctor as soon as you find out you pregnant, or if you only discover that you are expecting a bit late. An early scan is particularly important however, if: The ultrasound doctor may see a small gestation (pregnancy) sac that looks like a black hole because it is filled with fluid.
This scan estimates the risk of Down's syndrome and other chromosomal or structural abnormalities.
The scan is also used to check: The doctor may also check your cervix at this time.
Usually two scans are done during the first trimester.