What is the combined first-trimester screening test?
In short
- The combined test is a blood test plus an ultrasound scan, done around the same time, to estimate the chance of Down's syndrome and similar conditions.
- The blood test is usually done from about 10 weeks, and the ultrasound (measuring the fluid at the back of your baby's neck) between 11 and 14 weeks.
- Together they give you a chance, like 1 in 500 — not a yes/no diagnosis.
- Your doctor will explain your result and what further testing, if any, is available.
What happens
- A blood sample is taken from your arm.
- An ultrasound measures the fluid space at the back of your baby's neck, usually at the same visit as your dating scan.
- The blood result and the scan measurement are combined into one chance figure, along with your age and other details.
Baby's sex is never revealed
It is illegal in India for anyone -- including your sonographer -- to reveal, or help you find out, the sex of your baby before birth. This is the Pre-Conception and Pre-Natal Diagnostic Techniques (PCPNDT) Act, 1994.
Pre-Conception and Pre-Natal Diagnostic Techniques (PCPNDT) Act, 1994. Read the Act (India Code).
The details: numbers and where they differ
In the source's own words
The first screening test for Down's syndrome, Edwards' syndrome and Patau's syndrome is called the combined test. There are 2 parts to the combined test: a blood test when you're between 10 and 14 weeks pregnant, with blood taken from your arm; an ultrasound to measure the fluid at the back of your baby's neck during your 12-week scan (dating scan), when you're between 11 and 14 weeks pregnant.
NHS (UK), Screening for Down's syndrome, Edwards' syndrome and Patau's syndrome. Quoted verbatim.
The numbers
| Measure | Value | Source |
|---|---|---|
| Combined test blood sample window (pregnant women (NHS, UK)) | 10–14 weeks gestation | NHS (UK) |
| Combined test ultrasound (NT) window (pregnant women) | 11–14 (NHS) / 10–13 (ACOG) weeks gestation | NHS (UK) |
When to call your doctor
- If you're unsure whether you've been offered this test or when it's scheduled.
- If your result comes back higher chance and you want to discuss further testing options.
Discuss your results with your doctor: this page reports what these sources say, not advice for your situation.
Sources
- NHS (UK), Screening for Down's syndrome, Edwards' syndrome and Patau's syndrome. Quoted verbatim. OGL-style NHS content, free reuse with attribution.
- American College of Obstetricians and Gynecologists (ACOG), Prenatal Genetic Screening Tests (Patient FAQ). Named as the guideline this section describes; its text and tables are not reproduced here (All rights reserved (cite only)). Describes both first-trimester tests as usually done together between 10 and 13 weeks.
Sources checked 2026-09-26. How we source and check every page.
Educational summary of named sources, not medical advice.