Should I have genetic testing if I'm pregnant and over 35?

If you’re pregnant at 35 or older, your midwife or GP will discuss screening for chromosome conditions during your booking appointment. The chance of having a baby with Down’s syndrome, Edwards’ syndrome, or Patau’s syndrome increases with maternal age, but most babies born to mothers over 35 are healthy. Understanding your options helps you make the decision that’s right for your family.

Why age matters for chromosome conditions

Chromosome conditions happen when a baby has too many or too few chromosomes. The most common is Down’s syndrome (trisomy 21), where the baby has three copies of chromosome 21 instead of two. Edwards’ syndrome (trisomy 18) and Patau’s syndrome (trisomy 13) are rarer but more severe.

The chance of having a baby with Down’s syndrome rises with age. It’s estimated at around 1 in 350 at age 35, around 1 in 100 by age 40, and around 1 in 30 by age 45. These are population estimates, and your own chance also depends on other factors. The chance increases because eggs have been in the ovaries since before birth, and errors in cell division become more common as eggs age.

Age is just one factor. Many babies with Down’s syndrome are born to mothers under 35, simply because younger women have more babies overall. The NHS offers screening to all pregnant women, regardless of age.

NHS screening: what’s available

The NHS offers two types of screening during pregnancy:

Combined test (10–14 weeks). This combines a blood test measuring two pregnancy hormones with an ultrasound scan that measures fluid at the back of the baby’s neck (called the nuchal translucency). The results are combined with your age to give a chance score. The combined test is the more accurate of the two NHS screening tests for Down’s syndrome.

Quadruple test (14–20 weeks). If you book later in pregnancy, this blood test measures four hormones. The NHS notes it is not as accurate as the combined test for detecting Down’s syndrome.

Both tests give a chance score, not a yes-or-no answer. If your result shows a higher chance (1 in 150 or greater), you’ll be offered a further test. This may be:

• Non-invasive prenatal testing (NIPT) - a more accurate screening blood test, now offered on the NHS after a higher-chance result, or
• A diagnostic test, which can give a definite answer:
  • Chorionic villus sampling (CVS) at 11–14 weeks, or
  • Amniocentesis at 15 weeks onwards.

Diagnostic tests analyse cells from the placenta or amniotic fluid and give a definite answer. They carry a small risk of miscarriage. The NHS puts the chance of miscarriage after amniocentesis at around 1 in 200, with the risk for CVS broadly similar. More recent studies suggest the procedure-related risk may be lower than this - a 2019 systematic review estimated it at around 0.3% (roughly 1 in 300) for amniocentesis - though estimates vary and your own team will explain the risk for your situation.

Private NIPT: an alternative

Non-invasive prenatal testing (NIPT) analyses fragments of the baby’s DNA that circulate in your blood from about 9–10 weeks of pregnancy. A simple blood sample is all that’s needed.

NIPT is generally more accurate than the NHS combined test for Down’s syndrome. A systematic review found that, across studies, NIPT detected around 99% of babies with Down’s syndrome, with a very low false-positive rate - meaning fewer people are told they have a higher chance when their baby is actually unaffected. Accuracy can be lower in twin pregnancies, and no screening test is 100% accurate.

NIPT screens for:

• Trisomy 21 (Down’s syndrome)
• Trisomy 18 (Edwards’ syndrome)
• Trisomy 13 (Patau’s syndrome)

Some expanded panels also screen for:

• Sex chromosome conditions (like Turner syndrome or Klinefelter syndrome)
• Microdeletions (small missing pieces of chromosomes, such as 22q11.2 deletion syndrome)

NIPT is a screening test, not a diagnostic test. A higher-chance result still needs confirming with CVS or amniocentesis before any decisions are made.

The NHS now offers NIPT as a follow-up test for people with higher-chance combined-test or quadruple-test results. Private NIPT is available from around 9 weeks and typically costs between £300 and £600, depending on the panel.

How to decide

There’s no right or wrong answer. Some questions to consider:

What would you do with the information? Some people want as much information as possible, even if it doesn’t change their pregnancy plans. Others prefer not to know unless they would consider ending the pregnancy or want time to prepare for a baby with additional needs.

How do you feel about the NHS screening accuracy? The combined test does not detect every affected pregnancy. If that uncertainty feels manageable, NHS screening may be enough. If you want more certainty before deciding whether to have a diagnostic test, NIPT may suit you better.

How do you feel about diagnostic-test risks? The small miscarriage risk from amniocentesis or CVS is real. NIPT’s higher accuracy means fewer people go on to need diagnostic testing.

What’s your budget? NHS screening is free. Private NIPT costs several hundred pounds. Only you can decide if that’s affordable and worthwhile.

Do you want information about rarer conditions? Standard NIPT panels focus on the three main trisomies. Expanded panels cover microdeletions and sex chromosome conditions, but these are much rarer and the clinical significance isn’t always clear.

Your midwife or GP can’t tell you what to do, but they can talk through your options. You can also contact a genetic counsellor for a more detailed discussion.

What you can do at Jeen

Jeen offers several NIPT options from 9 weeks of pregnancy, all with a free midwife consultation before you take the test. Our midwife will talk through what each test covers, help you decide if screening is right for you, and answer any questions.

If you want the most comprehensive screen available, Panorama Microdeletions covers 13 conditions including microdeletions (small missing chromosome pieces like 22q11.2 deletion syndrome and 1p36 deletion syndrome). It has a high detection rate for trisomy 21 and results typically arrive in 7-10 working days from when your sample reaches the laboratory. This test is available from 9 weeks.

If speed matters most-for example, if you’re close to the 10-week booking deadline or want results quickly to decide about diagnostic testing-PrenatalSafe 3 UK screens for the three main trisomies with a 2-4 working day turnaround from when your sample reaches the laboratory, one of the fastest available. Results are reviewed by your midwife, with specialist follow-up arranged if you have a higher-chance result. This test is available from 10 weeks.

We also offer mid-range panels:

• Panorama NIPT: a 9-condition panel, available from 9 weeks with optional fetal sex reveal (high accuracy for the main trisomies).
• Niptify NIPT: a 30-condition panel covering sex chromosome conditions and some microdeletions, available from 10 weeks.
• Aneuploidy NIPT: a standard 3-condition screen (the three main trisomies), available from 9 weeks.

All results are returned with clinical interpretation, and your midwife will contact you to explain what they mean. If you have a higher-chance result, we’ll arrange specialist genetic counselling or diagnostic testing through the NHS.

You can have private NIPT as well as NHS screening, or instead of it. The blood draw isn’t included in the test price: you can arrange your own at no extra cost, or we can arrange a draw at a partner collection point (+£40) or a home-nurse visit (+£65). Book online or call to speak to our team.