Nuchal Translucency Ultrasound
Among all pregnancy tests, the nuchal translucency ultrasound, also known as the first-trimester or Level I ultrasound, holds a special place.
It is not simply an image of the fetus; it is an advanced diagnostic tool that, combined with biochemical blood tests, gives us a valuable first assessment of your baby’s health and development.
It is performed between the 11th and 13th week + 6 days of pregnancy.
What is nuchal translucency and why do we measure it?
Nuchal translucency (NT) is a thin layer of fluid that normally accumulates at the back of the neck of every fetus during the first trimester. With ultrasound, we accurately measure the thickness of this layer.
Why is this important?
Because increased nuchal translucency thickness has been associated with an increased risk of chromosomal abnormalities, mainly trisomy 21 (Down syndrome), but also trisomies 18 and 13, as well as certain heart defects.
The measurement alone does not provide a diagnosis, but when combined with other factors it reliably calculates the individual risk for each pregnancy.
Important: increased nuchal translucency does not automatically mean there is a problem. It means that further evaluation is needed, and this is always done calmly and with scientific documentation.
What does the first-trimester ultrasound include?
The nuchal translucency ultrasound is much more than a simple measurement. During the examination, we assess the following overall:
Nuchal translucency measurement (NT)
The central measurement of the examination, performed with a strictly standardized technique according to the protocols of the Fetal Medicine Foundation (FMF).
Nasal bone
Absence or hypoplasia of the nasal bone at 11–14 weeks is an additional risk marker for trisomy 21. Its assessment significantly enhances the predictive value of the examination.
Fetal anatomical assessment
We assess the development of the brain, spine, stomach, bladder, limbs, and heart at this stage—although the detailed anatomical examination will be completed during the Level II ultrasound.
Cardiac activity & rhythm
We confirm normal fetal cardiac function.
Crown-rump length (CRL)
We remeasure the CRL to confirm or revise gestational age with the greatest possible accuracy.
Placenta & amniotic fluid
We assess the position and appearance of the placenta, as well as the amount of amniotic fluid.
Cervix
In selected cases, we also measure cervical length as an early indicator of the risk of preterm birth.
First-trimester combined screening – the “combined test”
The nuchal translucency ultrasound achieves its maximum diagnostic value when combined with biochemical blood tests—specifically measurement of PAPP-A (pregnancy-associated plasma protein A), free β-hCG, and PLGF (Placental Growth Factor) from the mother’s blood.
The PLGF marker has particular clinical value because it allows early assessment of the risk of developing preeclampsia—a serious but common condition of pregnancy. Early identification of high risk makes preventive intervention possible, such as starting low-dose aspirin, which has been shown to significantly reduce the risk of developing it.
This combination, together with the mother’s age and gestational age, is calculated using specialized Fetal Medicine Foundation software and provides an individualized risk estimate for the major chromosomal abnormalities. The sensitivity of the method reaches 90–95% for trisomy 21, with a false-positive rate of only 5%.
How do I prepare for the combined test?
No special preparation is required. It is recommended that the blood sample be taken during the examination or a few days before the ultrasound, so that the results are available on the same day and the combined calculation can be performed immediately.
How is the examination performed and what should you expect?
The nuchal translucency ultrasound is usually performed transabdominally, with the probe on the abdomen, as at 11–14 weeks the fetus is large enough to be clearly visualized externally. In some cases (e.g., increased body weight or an unfavorable fetal position), it may be supplemented with a transvaginal ultrasound.
The examination lasts 20–30 minutes and requires some patience. The fetus must be in an appropriate position to obtain the correct measurement plane. Sometimes the patient needs to change position or walk a little so that the baby moves.
Preparation before the nuchal translucency scan
For a transabdominal ultrasound, it is recommended to have a moderately full bladder (that is, to drink about 2–3 glasses of water 30–40 minutes before the examination and not urinate).
A full bladder helps improve visualization of the uterus and the fetus.
Fasting is not required. You may eat normally. In fact, a light meal shortly beforehand may help the baby be more “active” so that we can more easily obtain the appropriate position.
If you are taking medication, continue it as usual and mention it during the examination.
Can I find out the baby’s sex?
This is one of the most common questions during the first-trimester ultrasound, and the answer is: sometimes yes, but not with certainty.
At 11–14 weeks, the external genital organs of the fetus have not yet fully differentiated. Experienced sonographers can make an estimate based on the angle of the genital tubercle, but the reliability of this estimate is about 70–75%—not high enough for a certain answer.
Reliable visualization of fetal sex is possible after the 16th–18th week, and with certainty at the Level II ultrasound (20th–22nd week). If you want to know earlier with high reliability, the NIPT (non-invasive prenatal testing) option can provide an answer from the 10th week.
What happens if the result is “high risk”?
A high-risk result is not a diagnosis; it is an indication for further investigation.
The next steps are always assessed on an individualized basis and may include:
- NIPT (Non-Invasive Prenatal Testing): analysis of fetal DNA from the mother’s blood (high reliability, with no risk to the pregnancy).
- Amniocentesis: an invasive test that provides a definitive diagnosis through karyotyping (discussed only when there are strong indications).
The decision for each next step is always made by the couple, with full information and without pressure.
Frequently Asked Questions (FAQ)
It is the most effective non-invasive first-trimester prenatal screening method.
It is not legally mandatory, but it is strongly recommended by all international obstetric societies.
The examination cannot be performed after the 14th week. However, there are alternatives, such as the second-trimester triple test or NIPT. Contact your doctor immediately to evaluate your options.
No. The transabdominal ultrasound is completely painless. The only “difficulty” may be the feeling of a full bladder during the examination.
It depends on whether the biochemical blood screening has been done in advance. If the PAPP-A and β-hCG results are already available on the day of the ultrasound, the combined calculation is performed on the spot and you leave with a complete picture the same day. If the blood tests are done at the same time as the ultrasound, the results are usually issued within 1–2 working days.
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