What is an ultrasound?
Ultrasound uses harmless sound waves to make pictures of how your baby is growing and developing. In an ultrasound exam the health care provider moves a handheld device, called a transducer, along your abdomen. To get a clearer picture, your abdomen is covered with a thin layer of gel. The transducer sends sound waves into your womb. A computer gathers the information from these sound waves to make a live picture of the baby seen on a monitor.
The ultrasound exam is painless. Ultrasound is available only when requested by your health care provider.
When are ultrasounds done, and what can be seen on an ultrasound?
Some women are booked for an ultrasound early (before 14 weeks) in pregnancy to check the baby’s heartbeat, see if there is more than one baby, and check how far along the pregnancy is by measuring the size of the baby. Most detailed ultrasounds are booked between 18 - 20 weeks of pregnancy
What is a nuchal translucency (NT) ultrasound?
A nuchal translucency (NT) ultrasound measures a fluid-filled space at the back of your baby’s neck. The NT scan is done between 11 and just under 14 weeks of pregnancy.
NT ultrasound is one part of an Integrated Prenatal Screening (IPS), involving two blood tests, which can be done in women carrying a single or twin pregnancy. The combination of the NT ultrasound and the two blood tests tell you the chance of your baby having Down syndrome, trisomy 18 or an open neural tube defect. Your health care provider will have your screen result within ten days after the second blood test.
NT ultrasound alone may be done in women carrying triplets or more.
How is an NT ultrasound done?
The main part of an NT ultrasound involves an ultrasound scan. To accurately date your pregnancy, the sonographer will measure your baby from the top of its head to the bottom of the spine (called a Crown Rump Length (CRL) measurement). The sonographer will then measure the width of the fluid-filled space at the back of the baby's neck. The skin will appear as a white line, and the fluid under the skin will look black.
Given that many problems cannot be detected at this stage of pregnancy, an ultrasound at 18-20 weeks is recommended and can be arranged by your health care provider.