Blood tests in pregnancy: what they check and when

You’ll have blood taken more than once in pregnancy, and it can be hard to keep track of why. Here’s what the main blood tests check, when they happen and what you can ask.

The blood tests you’ll be offered

At your first (booking) appointment with a midwife, which the NHS puts at around 8 to 12 weeks, you’ll be offered a number of blood tests. The NHS says one checks your blood group. You’ll also be offered screening for several conditions, and you can say yes or no to each one.

Blood group and rhesus status. This shows whether you are rhesus (D) negative. If you are, and your baby is D positive, you could make antibodies that break down your baby’s red blood cells, so you may be offered an anti-D injection. See rhesus negative and anti-D.
Hepatitis B, HIV and syphilis screening. One blood test for three infections. You can choose any or all of them. Read more in screening for HIV, hepatitis B and syphilis in pregnancy.
Sickle cell and thalassaemia screening. Thalassaemia screening is a blood test offered to everyone, and sickle cell screening starts with a questionnaire. See sickle cell and thalassaemia screening.
Iron levels (anaemia). The NHS lists a check of your health and iron levels at 28 weeks. Some trusts check at booking too, so ask your midwife. See anaemia and iron tests in pregnancy.

Some people are also offered a test for gestational diabetes, usually between 24 and 28 weeks, if they have a higher chance of developing it. Read everything you need to know before your gestational diabetes test.

Timing

The NHS says screening for infections should be done as early as possible, ideally by 10 weeks, and sickle cell and thalassaemia screening is recommended before 10 weeks, though it can be done at any time. That’s why your midwife may suggest doing the bloods at your booking appointment. If you’ve missed it, ask for them anyway.

What it’s like

The NHS says a healthcare professional usually takes blood from the inside of your elbow with a needle, and it takes about 10 minutes. You’ll feel a scratch and may get a little bruising that fades in a few days. If you’re nervous about needles, tell the staff and bring someone with you if you can.

Getting your results

How results reach you depends on your trust and on which test it is. For sickle cell and thalassaemia, the NHS says most people are told at their next antenatal appointment, and if you’re a carrier you’ll be contacted as soon as possible and offered an appointment to talk it through. Ask your midwife how and when you’ll hear about each test, and note it in your maternity notes. If you haven’t heard when you expected to, contact your midwife or maternity unit.

It’s your choice

Screening is offered to everyone, and you can decline any part of it. It’s worth asking your midwife what each test is for before you decide. If you’re worried about a result, Antenatal Results and Choices (ARC) offers support after a screening result: 020 7713 7486, Monday to Friday, 10am to 5.30pm.

Questions people ask

Do I have to have all of these blood tests?

No. They’re offered to everyone, but it’s your choice to have any or all of them.

What if I miss the 10 week window?

You can still have the tests. The NHS says sickle cell and thalassaemia screening can be done at any time, and that if you decline infection screening you’ll be offered it again before 20 weeks.

Will blood tests hurt my baby?

The NHS says there are no known risks to you or your baby from the sickle cell and thalassaemia blood tests.

Who do I call if I haven’t had my results?

Your midwife or maternity unit. See what to do if you can’t get hold of your midwife.