Before this the scan is difficult to do because your baby is still so tiny.
Nuchal scan vs dating scan
Abdominal scanning is performed with a full maternal bladder, provides a wider field of view, and provides the greatest depth of view.
Vaginal scanning is best performed with the bladder empty, gives a much greater resolution with greater crispness of fine detail.
However, diagnostic tests do carry a small risk of miscarriage.
An NT scan can't tell you for certain whether or not your baby is affected.
A nuchal translucency (NT) scan is a screening test that assesses whether or not your baby is likely to have Down syndrome.