First, to help the doctor be absolutely precise when inserting the needle, an ultrasound scanner is used to establish the exact position of the fetus and the placenta. Second a fine needle is inserted into the womb and into a pool of amniotic fluid.

"Nuchal" means neck; nuchal ultrasound is carried out at 11 to 14 weeks to look at thickness of a certain area at the back of the fetus'' neck. A particularly thick nuchal pad has been linked with a higher risk of suffering from heart defects, Down syndrome, or some other chromosomal problem. A nuchal scan may follow or be followed by an AFP₃, or Triple test, to gain more insight into possible problems. Subsequent amniocentesis, or another invasive diagnostic procedure will help confirm or rule out these problems. Ask your doctor for a complete explanation of all procedures.

What the scan shows The picture shows a normal fetus. The dotted lines indicate where the nuchal pad would be thicker, as in Down syndrome.