Babies with abnormalities tend to accumulate more fluid at the back of their neck during the first trimester, causing this clear space to be larger than average. The NT scan must be done when you're between 11 and 14 weeks pregnant, because this is when the base of your baby's neck is still transparent.
(The last day you can have it is the day you turn 13 weeks and 6 days pregnant.) It's usually offered along with a blood test in first-trimester combined screening options.(Some practitioners also look for the presence of the fetal nasal bone in the first trimester.
Some hospitals or private ultrasound centres have a policy of not telling women the sex of their baby, as it is often not possible to be certain.
18 - 20 week pregnancy ultrasound Dating scans Ultrasound variants in pregnancy What is a placental lake?
Scans to check the position of the placenta What is a fetal echo? Why am I being offered a third trimester growth scan?
The screening is widely available, but because it requires special training and equipment, not all healthcare providers provide it.(Women who are at high risk for carrying a child with Down syndrome or are 35 or older may be offered cell-free DNA testing, which can be done as early as 10 weeks.
Scans after 20 weeks A guide to ultrasound: video Pregnancy ultrasound scans: an overview When will I be able to find out my baby's gender on a scan?
Nuchal translucency (NT) scan Can I have a nuchal ultrasound if I'm expecting twins?