Pregnancy is a time when many people have questions about the health and development of their baby. Genetic testing during pregnancy covers a range of screening and diagnostic procedures designed to provide information about certain chromosomal or genetic conditions. Understanding what these tests involve, when they can be performed, what they can and cannot tell you, and how NHS and private pathways differ can help you make informed decisions with the support of your healthcare team.
This article explains the main types of prenatal genetic testing available in the UK, the differences between screening and diagnostic testing, how first-trimester screening works, private options, costs, result timelines, and what happens when a higher-chance result is returned.
What Is Genetic Testing During Pregnancy?
Genetic testing during pregnancy refers to tests that examine a baby's chromosomes, genes or DNA to look for certain conditions. Some of these tests screen for the likelihood of a condition being present, while others are diagnostic and can confirm or rule out a specific diagnosis.
Chromosomal conditions arise when there are changes in the number or structure of chromosomes. Down's syndrome (trisomy 21), Edwards' syndrome (trisomy 18) and Patau's syndrome (trisomy 13) are among the most commonly screened-for chromosomal conditions in pregnancy. Genetic conditions may also result from changes in individual genes, which may be inherited from one or both parents.
It is important to understand that no single test screens for every chromosomal or genetic condition. Tests are designed to look for specific conditions, and results must always be interpreted alongside appropriate clinical guidance. Testing is voluntary, and any decision about whether to test is personal and should be made with full information and professional support.
Genetic Screening vs Diagnostic Testing: An Important Distinction
Screening and diagnostic testing are not the same thing, and understanding the difference is essential.
Screening tests assess the probability that a baby has a particular condition. They do not confirm a diagnosis. A result described as "lower chance" means the probability is lower but does not guarantee that the condition is absent. A result described as "higher chance" means the probability is elevated but does not mean the baby definitely has the condition. Screening tests are non-invasive or minimally invasive and carry no direct procedural risk to the pregnancy.
Diagnostic tests are designed to confirm or rule out a specific chromosomal or genetic condition. They analyse fetal cells or tissue directly. These include:
Both procedures carry a small risk of pregnancy loss, estimated at approximately 0.5–1% depending on the procedure and clinical setting. They are typically offered following a higher-chance screening result or in specific clinical circumstances. The decision to proceed with diagnostic testing should always be discussed with an appropriately qualified healthcare professional.
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First-Trimester Screening: The Combined Test
First-trimester screening in the UK most commonly takes the form of the combined screening test, which is part of the NHS fetal anomaly screening programme. It is typically offered between 11 weeks and 13 weeks and 6 days of pregnancy.
The combined test brings together two components:
The results of both components, alongside factors such as age and gestational age, are combined to calculate a statistical chance for Down's syndrome, Edwards' syndrome and Patau's syndrome. Results are reported as a ratio (for example, 1 in 150 or 1 in 10,000) and categorised as either lower chance (below 1 in 150) or higher chance (1 in 150 or above) for Down's syndrome under NHS guidance.
The combined test is the most effective first-trimester screening approach available through the NHS, detecting approximately 85–90% of pregnancies affected by Down's syndrome, though this figure can vary. It does not screen for all genetic or chromosomal conditions.
When Can Genetic Testing Be Done in Pregnancy?
The timing of genetic testing depends on the specific test, gestational age and clinical circumstances. There is no single point in pregnancy when all tests can be performed simultaneously.
| Test | Approximate Timing |
|---|---|
| Combined screening test (first-trimester screening) | 11–13+6 weeks |
| Non-invasive prenatal testing (NIPT) | Usually from 10 weeks |
| Chorionic villus sampling (CVS) | 11–14 weeks |
| Quad/quadruple screening test (second-trimester) | 14–20 weeks |
| Amniocentesis | Usually from around 15 weeks |
| Anomaly ultrasound scan | Around 18–21 weeks |
Timing windows exist because certain markers are only measurable at specific gestational ages and because the reliability of measurements varies by stage of pregnancy. If a person books antenatal care late, some first-trimester options may no longer be available, and different pathways apply.
NHS Genetic Testing During Pregnancy
The NHS offers a structured antenatal screening programme as part of routine maternity care in England. The relevant framework is set out by the NHS Fetal Anomaly Screening Programme (FASP).
Under this programme, screening for Down's syndrome, Edwards' syndrome and Patau's syndrome is routinely offered to all pregnant people in England. The combined test is the preferred first-trimester screening approach, though if this window has passed, a different blood test (the quadruple test) is offered between 14 and 20 weeks.
Following a higher-chance combined test result, the NHS now offers NHS NIPT (non-invasive prenatal testing) as a further screening step before diagnostic testing is considered. This was introduced as part of the FASP pathway following national evaluation and expanded rollout. However, it is important to note that NHS NIPT is a further screening test, not a diagnostic test.
Screening for sickle cell disease and cystic fibrosis carrier status is also offered through the NHS at different stages of pregnancy, alongside screening for conditions such as HIV, hepatitis B and syphilis. Not all genetic conditions are routinely screened for on the NHS, and the programme does not cover every chromosomal or inherited condition.
Participation in NHS screening is always voluntary. Midwives and obstetricians are available to discuss the choices involved.
Private Genetic Testing During Pregnancy
Private prenatal genetic testing may appeal to people who wish to access testing that is not routinely available on the NHS pathway, who want results within a different timeframe, or who are seeking additional options for personal reasons.
The most commonly sought private prenatal genetic test in the UK is non-invasive prenatal testing (NIPT), sometimes referred to by brand names such as Harmony, Panorama or IONA. Private NIPT analyses cell-free fetal DNA circulating in the pregnant person's blood and can screen for chromosomal conditions including Down's syndrome, Edwards' syndrome and Patau's syndrome, as well as certain sex chromosome conditions. Some versions screen for a broader range of chromosomal variants.
When considering private genetic testing during pregnancy, it is important to:
Private providers vary considerably in their scope of services, laboratory arrangements and support. It is advisable to ask these questions before booking.
For a broader overview of private health screening options, you may find it useful to explore the health screening services at Private Blood Tests London.
Genetic Screening Before Pregnancy: Carrier Testing
Carrier screening is a type of genetic testing that can be done before conception to find out whether one or both partners carry a gene variant associated with certain inherited conditions. Carrier screening does not indicate whether a person will develop the condition themselves, but can inform reproductive decisions if both partners are found to carry a variant for the same recessive condition.
Conditions commonly included in preconception carrier screening panels include cystic fibrosis, spinal muscular atrophy (SMA), sickle cell disease, thalassaemia and fragile X syndrome, among others.
In the UK, NHS carrier screening for sickle cell disease and thalassaemia is offered during pregnancy as part of the routine antenatal programme. Preconception carrier screening beyond this is not comprehensively offered on the NHS for the general population, though referral through a GP or specialist may be available in certain circumstances, particularly where there is a known family history.
Private preconception carrier screening panels are available in the UK through specialist providers and some private clinics. These tests are distinct from tests performed during pregnancy and cannot tell you anything about the chromosomal status of an existing pregnancy.
Can Genetic Testing Tell You the Baby's Sex?
Some prenatal tests can report fetal sex as part of their results. Cell-free fetal DNA tests such as NIPT can detect the presence or absence of a Y chromosome, which may indicate the baby's biological sex.
However, whether sex information is reported depends on:
Sex is not routinely reported by the NHS as part of its screening programme, though the anomaly ultrasound scan (around 18–21 weeks) may show the baby's genitalia. Some NHS trusts will share this information if asked, while others do not.
If knowing the baby's biological sex is important to you, confirm before booking whether the specific test and provider include sex reporting, and at what gestational age results can be reliably returned.
How Much Does Private Genetic Testing During Pregnancy Cost?
The cost of private prenatal genetic testing in the UK varies according to the type of test, the provider and what is included in the package (for example, whether a consultation and ultrasound are included alongside the blood draw).
As a general guide at the time of writing:
These figures are indicative only. Costs change over time and vary between providers. Always request a detailed breakdown of what is included before proceeding. For information about private test pricing at Private Blood Tests London, you can visit the blood test prices page.
How Long Do Prenatal Genetic Test Results Take?
Turnaround times depend on the specific test and laboratory processing arrangements.
These are approximate ranges and should not be taken as guarantees. Delays can occur due to sample quality, laboratory capacity or the need for repeat testing. Ask your provider for their specific estimated turnaround time at the point of booking.
Understanding Your Results and Next Steps
Receiving a prenatal screening result — whether lower chance or higher chance — can be emotionally significant. It is important to understand what the result does and does not mean.
Following any result that raises questions, it is important to speak with a midwife, obstetrician or genetic counsellor who can explain the findings, discuss the options and provide appropriate support. No screening result should be acted upon without qualified clinical interpretation.
Booking a Private Blood Test or Health Screen
If you are exploring private health testing options, Private Blood Tests London offers a range of private blood testing services. You can also book directly online or explore the full range of health screening packages available.
Where prenatal or genetic testing is specifically required, always confirm that the provider offers the specific test you are seeking and that appropriate clinical support is in place.
Frequently Asked Questions
What is genetic testing during pregnancy?
Genetic testing during pregnancy encompasses a range of screening and diagnostic procedures that examine chromosomes or genes to assess whether a baby may be at higher chance of, or has been diagnosed with, certain genetic or chromosomal conditions. Tests vary in their purpose, timing and method.
How many weeks pregnant do you need to be for genetic testing?
This depends on the specific test. First-trimester combined screening is performed between 11 and 13 weeks and 6 days. Private NIPT is usually available from around 10 weeks. The quadruple screening test is offered between 14 and 20 weeks, and amniocentesis is usually performed from around 15 weeks. There is no single universal timing that applies to all tests.
What is the combined screening test?
The combined screening test is the main first-trimester screening test offered through the NHS in England. It combines a blood test measuring PAPP-A and hCG with a nuchal translucency ultrasound measurement to calculate the statistical chance of Down's syndrome, Edwards' syndrome and Patau's syndrome. It is performed between 11 and 13 weeks and 6 days of pregnancy.
Is NIPT a diagnostic test?
No. Non-invasive prenatal testing (NIPT) is a screening test, not a diagnostic test. It analyses cell-free fetal DNA in the pregnant person's blood and can detect a higher or lower chance of certain chromosomal conditions, but it cannot confirm a diagnosis. A higher-chance NIPT result should be followed up with diagnostic testing (CVS or amniocentesis) if a confirmed diagnosis is needed.
Is genetic testing available on the NHS during pregnancy?
Yes. The NHS offers structured antenatal screening for chromosomal conditions including Down's syndrome, Edwards' syndrome and Patau's syndrome as part of the NHS Fetal Anomaly Screening Programme. Following a higher-chance combined test result, NHS NIPT is now also offered as a further screening step. Carrier screening for sickle cell disease and thalassaemia is also available. Not all genetic tests are routinely offered on the NHS.
Can you get genetic testing privately during pregnancy in the UK?
Yes. Private NIPT and other prenatal screening options are available through private providers across the UK. Private testing may allow access to additional screening options, different appointment arrangements or, in some cases, faster access to results. It is important to verify what the specific test covers, what support is available and what costs are involved before booking.
How much does private pregnancy genetic testing cost in the UK?
Costs vary by test and provider. Private NIPT typically ranges from around £350 to £800 or more depending on the panel. Costs for other tests differ significantly. Always confirm what is included in the quoted price, including consultations, ultrasounds and post-result support.
How long do prenatal genetic test results take?
Turnaround times vary. Private NIPT results are often available within approximately five to fourteen working days. NHS combined screening results are typically returned within one to two weeks. Rapid diagnostic results from CVS or amniocentesis for the most common chromosomal conditions are often available within two to three working days, with full results taking longer. Confirm expected timings with your specific provider.
Can genetic testing tell you the sex of the baby?
Some tests, including NIPT, can detect fetal sex by identifying the presence or absence of a Y chromosome. Whether sex information is reported depends on the specific test, the laboratory and provider policy, and whether you have requested it. Sex is not routinely reported as part of NHS screening. Confirm with your provider whether sex reporting is available and at what gestational age.
What is the difference between CVS and amniocentesis?
Both are invasive diagnostic tests that can confirm or exclude chromosomal conditions with greater certainty than screening tests. CVS involves taking a small sample of placental tissue and is usually performed between 11 and 14 weeks. Amniocentesis involves sampling amniotic fluid and is usually performed from around 15 weeks. Both carry a small risk of pregnancy loss and should only be considered following appropriate clinical assessment and counselling.
Can genetic screening be done before pregnancy?
Yes. Preconception carrier screening allows individuals or couples to find out whether they carry gene variants associated with certain inherited conditions, such as cystic fibrosis, sickle cell disease or spinal muscular atrophy. This type of screening is distinct from tests performed during pregnancy and can help inform family planning decisions. Availability and scope vary between NHS and private providers.
What should I do if I receive a higher-chance screening result?
A higher-chance result does not mean your baby has been diagnosed with a condition. It means the statistical probability is elevated and that further discussion is recommended. Contact your midwife, obstetrician or genetic counsellor as soon as possible. They can explain the result in context, discuss diagnostic options such as CVS or amniocentesis, and provide appropriate support. Decision-making at this stage is personal and should be fully informed.
Medical References and Further Information
This article is intended for general informational purposes only. It does not constitute medical advice and should not be used as a substitute for professional clinical guidance. If you have specific concerns about genetic testing during pregnancy, speak with your GP, midwife or a qualified specialist.