Screening tests offered in pregnancy in the UK

What you are offered

The NHS offers a defined set of antenatal screening tests, free, to everyone who is pregnant in the UK. Screening does not diagnose anything. It sorts pregnancies into lower chance and higher chance, and a higher-chance result is an invitation to a further test, not a finding.

Every one of these tests is optional. The NHS states it plainly: you can choose to have all of them, some of them, or none. You can also change your mind and have a test later, subject to the gestational windows below. Declining screening does not affect the rest of your maternity care.

Infectious diseases — from 8 to 12 weeks

A single blood sample at your booking appointment is screened for HIV, hepatitis B and syphilis. All three are treatable in pregnancy, and treatment substantially reduces the chance of passing the infection to your baby. This is the screening with the clearest benefit and the lowest cost to you, which is why it is offered to everyone at every pregnancy regardless of perceived risk.

Sickle cell and thalassaemia — ideally before 10 weeks

A blood test screens for these inherited blood disorders. It is offered as early as possible — ideally before 10 weeks — because if you are found to be a carrier, the baby's father is offered testing too, and that sequence takes time. Early booking is what keeps the full range of options open here.

Down's, Edwards' and Patau's syndromes — 10 to 20 weeks

Two tests are available and which one you get depends purely on how many weeks pregnant you are.

• The combined test is offered between 10 and 14 weeks. It has two parts: a blood test taken from your arm between 10 and 14 weeks, and a nuchal translucency ultrasound measurement taken between 11 and 14 weeks. They are usually done at the same visit. It screens for all three conditions.
• The quadruple test is offered instead if you are more than 14 weeks pregnant. It is a blood test done between 14 and 20 weeks. It screens for Down's syndrome only, and it is less accurate than the combined test.

That difference is the practical argument for booking early. Miss the 14-week boundary and you lose both accuracy and coverage of two of the three conditions.

The 20-week screening scan — 18 to 21 weeks

Sometimes called the anomaly scan, this ultrasound looks at the baby's physical development and screens for 11 specific conditions: anencephaly, open spina bifida, cleft lip, diaphragmatic hernia, gastroschisis, exomphalos, serious cardiac abnormalities, bilateral renal agenesis, lethal skeletal dysplasia, Edwards' syndrome and Patau's syndrome. It is normally done between 18 and 21 weeks, and can be done up to 23 weeks in some circumstances.

The scan is not a general health check and it does not find everything. Some of the 11 conditions are detected far more reliably than others, and conditions outside the list are not being looked for.

If a screening result comes back higher chance

You will be contacted by phone or in person within one week of the test if the result shows a higher chance of Down's, Edwards' or Patau's syndrome. You will then be offered a choice, and there is no obligation to take any of it:

• Non-invasive prenatal testing (NIPT) — a more accurate screening blood test that analyses fragments of the baby's DNA circulating in your blood. It is still a screening test, not a diagnosis.
• Chorionic villus sampling (CVS) or amniocentesis — diagnostic tests that sample placental tissue or amniotic fluid and give a definitive answer. Both carry a small risk of miscarriage, which your midwife or a fetal medicine specialist will quantify for your situation.

You are entitled to time to think, to a second conversation, and to decline further testing altogether. A higher-chance screening result is not a diagnosis and in most cases the baby does not have the condition.

What screening does not cover

NHS antenatal screening does not include general genetic carrier screening, whole-genome testing, or routine testing for cytomegalovirus, toxoplasmosis or group B streptococcus. Group B strep in particular is a common source of confusion: the UK does not screen for it routinely, and the NHS instead manages it through risk factors in labour. Private testing exists for several of these, and if you buy it you should tell your midwife so the results can be recorded properly and acted on within NHS pathways.

After the birth

Screening continues once the baby arrives. Within the first few days your baby is offered the newborn blood spot test (the heel prick), which screens for nine rare but serious conditions including sickle cell disease, cystic fibrosis and congenital hypothyroidism; a newborn hearing screen; and a newborn physical examination within 72 hours covering the eyes, heart, hips and testes. These are also optional, and also free.

Where to get help

The NHS is the governing authority for antenatal screening in the UK, and its screening pages set out each test, its window and what the results mean. Your midwife is the person who should talk you through any result before you decide anything, and you can ask to speak to a screening midwife or a fetal medicine specialist for a more detailed conversation. Antenatal Results and Choices (ARC) is an independent charity offering free, non-directive support to anyone making decisions after a screening result, including a helpline.