What does my NT measurement mean?

Nuchal translucency (NT) is a small, normal pocket of fluid at the back of every baby's neck, seen on ultrasound in the first trimester. It's measured as part of the first-trimester combined screen, usually between 11 and 14 weeks — most precisely from 11 weeks 0 days to 13 weeks 6 days, when the crown-rump length is about 45 to 84 mm. All babies have some nuchal fluid; the measurement is simply how thick that layer is on the day of the scan. A larger measurement raises the chance that a screening result comes back higher-risk, which is why it's noted — but on its own it's just one number.

No — take a breath. NT is a screen, not a diagnosis, and a measurement at or above the commonly used flags (around 3.0 mm, and especially 3.5 mm and up) does not mean anything is wrong. It means a closer look is worthwhile. The great majority of babies with a mildly increased NT are healthy, and even with a clearly increased NT many go on to be born healthy. What an increased NT does is open a conversation with your provider about the follow-up options — cell-free DNA (NIPT), a diagnostic test if you want certainty, and a fetal heart scan later — so you can get real information rather than sit with a single number.

Because your NT alone can't produce an honest one, and pretending otherwise would mislead you. A real first-trimester risk figure combines four things: the NT measurement, your age, and two blood markers — PAPP-A and free beta-hCG — run through software calibrated to your exact dating (crown-rump length). The same NT in millimetres also means different things at 11 weeks versus 13 weeks, because normal NT grows with the baby. So a millimetre reading on its own maps to a percentile, not a personal risk, and only your clinic's software — with your bloods and dating — produces the figure that counts. This tool gives you the plain-English category and what usually follows; your provider gives you the number.

Typically three things, and all are optional. First, cell-free DNA screening (NIPT) — a blood draw that's the most sensitive screen for Down syndrome and trisomies 18 and 13, though still a screen. Second, a diagnostic test — chorionic villus sampling (CVS, from about 10–13 weeks) or amniocentesis (from about 15 weeks) — which reads the baby's actual chromosomes and gives a definitive answer for the conditions tested, in exchange for a small procedure risk your provider will quantify. Third, a detailed fetal heart scan (fetal echocardiogram) later in pregnancy, because an increased NT is linked to a higher chance of heart differences even when the chromosomes are normal. A genetic counselor can walk you through which of these fit your situation.

They answer different questions. This tool reads a measurement you already have and tells you which category it falls into and what usually comes next. If you're deciding which prenatal test to have in the first place, our prenatal genetic screening chooser maps carrier screening, NIPT, the combined screen, CVS and amniocentesis to your dates and history. If you want the baseline chance of Down syndrome by maternal age — the age 'prior' that NT and bloodwork then refine — the Down syndrome chance-by-age tool covers that. And carrier screening, a separate two-partner test for inherited conditions, has its own page. They're designed to be used together, not to overlap.

Yes. This tool runs entirely in your browser. The measurement and week you enter are used on your own device to look up a plain-English category and are never sent to a server, saved, or shared — close the tab and they're gone. In a post-Dobbs world we treat reproductive data as sensitive by default, so there's no account and nothing to delete. It's general educational information based on published NT conventions and screening guidance; it is not medical advice, a diagnosis, a risk figure, or a prediction about your pregnancy.