What is the 11-13 week nuchal scan?
The nuchal scan appointment is the first important appointment in your pregnancy. This appointment will allow us to accurately date your pregnancy, undertake a survey of the baby’s anatomy and provide you with a risk assessment of Down’s syndrome and other chromosomal abnormalities. The scan is carried out from 11 weeks to 13 weeks and six days.
What are the objectives of this visit?
The main objectives of this visit are:
- Accurate dating of the pregnancy
- Diagnosis of multiple pregnancies
- Diagnosis of early pregnancy failure
- Diagnosis of major fetal abnormalities
- Screening for chromosomal abnormalities
How much time will the appointment take?
Usually, the scan will be completed in 45 minutes but in some instances, it may take up to an hour depending on the position of your baby and the adequacy of views obtained on the ultrasound scan.
Do I have to have a full bladder for the scan?
No, you do not need to have a full bladder for this appointment.
How will the scan be carried out?
The ultrasound examination will be carried out through your abdomen (transabdominal). Sometimes, it may be necessary to carry out an internal examination (transvaginal) if the necessary views to complete the scan cannot be obtained by abdominal scanning.
How will the risk of Down’s syndrome be assessed?
This assessment is based on your age, ultrasound scan and measurement of levels of specific proteins in your blood. The ultrasound scan will allow us to measure the baby’s length (crown rump length) and the nuchal translucency (thickness of fluid behind the baby’s neck). The blood sample obtained from you will allow us to measure two proteins in your blood (free beta-human gonadotropic hormone [β-hCG] and pregnancy associated plasma protein-A [PAPP-A]). These bloods will need to be done at either 10 weeks or up to 2 days before the scan itself. We will combine the results of the ultrasound scan and the blood tests and provide you with an individual and specific risk for your pregnancy.
What if I am deemed to be high-risk?
If the result of the combined test is high-risk, then the pros and cons of further management options will be discussed which include cell free DNA testing by taking a blood sample from the mother or an invasive test such as chorionic villus sampling (CVS) or amniocentesis.