NT scan and combined test: a result is a chance, not a diagnosis

Weeks 11–14 are a turning point: your baby now has a recognisable shape, and your doctor can for the first time estimate the chance of certain chromosomal conditions. This is not an exam; it is a step in gathering information.

What are the NT scan and combined test?

NT (nuchal translucency) is an ultrasound measurement of the thin fluid-filled space at the back of your baby's neck. The measurement is combined with two values from your blood (usually free beta-hCG and PAPP-A). This is called the combined test or first-trimester screening. In the Turkish Ministry of Health guideline, this screening is listed for weeks 11–14.

What does it look for?

The test estimates the chance of certain chromosomal conditions, mainly Down syndrome (trisomy 21), but also trisomy 18 and 13. A computer program uses your age, the NT measurement, the blood values and your baby's length together. The NT can also hint at some heart or structural differences.

How is it done?

The ultrasound is usually abdominal, painless and takes a few minutes. The blood sample can be taken on the same day or a few days earlier. The results reach your doctor within a few days. If your baby's position makes the measurement difficult, you may be asked to wait or move around a little.

How to read the result

The result is usually given as a fraction such as 1 in 1,000 and summarised as lower chance or higher chance.

• Lower chance: a condition is unlikely, though not impossible.
• Higher chance: this does not mean a condition is present; it only shows that more information is needed. Many pregnancies with a higher-chance result end with a healthy baby.

This is a screening test, not a diagnostic test. False alarms (false positives) and false reassurance (false negatives) are possible.

If the result is higher chance

You can take your time to talk with your doctor. Options include cell-free fetal DNA testing (NIPT), a detailed ultrasound, or invasive tests such as chorionic villus sampling or amniocentesis for a definite answer. You can read about them in the related article. Your doctor will also explain that invasive tests carry a small risk of miscarriage. Which way to go is a shared decision between you and your doctor; no path is right or wrong.

What you can do

• Before the test, think about what the result would mean to you; having it or not is a personal choice.
• Prepare your questions: the cut-off used, next steps, costs.
• While you wait, talk to your partner or someone you trust.
• With twins, interpretation can differ; ask your doctor.

When to contact your doctor

• If your result is higher chance, talk to your doctor without delay
• Vaginal bleeding or severe abdominal pain
• Fever, foul-smelling discharge or leaking fluid
• Bleeding, fever or fluid loss after an invasive test

In a sudden and serious situation, call 112. This article is for information only; for your personal situation, your doctor's advice comes first.