Combined screening in pregnancy: How the Different Measurements Fit Together

Combined screening brings together a blood test, an ultrasound measurement and information about you to estimate the chance of certain chromosome conditions. None of those pieces should be interpreted alone as a diagnosis. The complete result is what the screening team uses to discuss your options.

Understand what is combined

In the NHS England pathway, the test estimates the chance of Down’s syndrome, Edwards’ syndrome and Patau’s syndrome. The scan measures fluid behind the baby’s neck, called nuchal translucency. This is combined with blood markers and your age in the calculation.

The blood sample is usually taken between 10 and 14 weeks and the scan between 11 and 14 weeks. The team confirms the appropriate window for your pregnancy. If combined screening is no longer possible, a quadruple blood test may be offered between 14 and 20 weeks; it screens for Down’s syndrome only.

Confirm whether the blood and scan are booked separately. A dating scan invitation does not necessarily mean you have already chosen every screening option, so ask what will be offered that day.

Read a chance result carefully

A result such as one in 100 describes an estimated chance, not a diagnosis. A larger second number means a smaller chance: one in 1,000 is lower than one in 100. Ask the team to explain your own result in both numbers and words.

Lower chance does not mean impossible, and higher chance does not mean the baby definitely has a condition. Screening also cannot describe every aspect of an individual child’s future health or development. A reassuring result does not replace other planned pregnancy checks.

Discuss the next choices

After a higher chance result, the discussion can include more accurate screening with NIPT, a diagnostic test or no further testing. The NIPT guide explains why a second screening test still has limits.

Ask what each option would add to the information you already have, how long the result might take and whether waiting affects the choices available. The screening and diagnostic testing comparison can help you prepare those questions.

Make room for the conversation

Before the test, ask how results will arrive and when to contact the service if they are late. After a result, request the written report and a clear explanation of any unfamiliar terms. You can bring someone to the appointment if you would find that helpful.

It is reasonable to need time and support to understand the information. Ask which decisions have a timing window without feeling that every choice must be made in the first phone call. Your maternity care continues whatever screening choices you make.