Blood tests in pregnancy

What blood tests can you expect during pregnancy, and what are they testing for?


Booking-in tests

These are the tests that are usually carried out at your first ‘booking in’ appointment with your midwife. Your midwife will take blood for the following tests:
•    Blood group: If you need a blood transfusion during pregnancy or labour, doctors need to know what blood group you are. You might be O (the most common blood type), A, B or AB.
•    Rhesus (Rh) factor: Most people are Rh positive, meaning that they carry a protein on their red blood cells. People whose red blood cells don’t carry this protein are rhesus negative. Your rhesus factor isn’t important for your everyday health, but it’s significant during pregnancy if you’re rhesus negative. If you’re rhesus negative but your baby is rhesus positive, then you’ll need anti-D injections to protect your baby’s health.
•    Rubella (German measles): This checks whether you’re immune to rubella or not. If you’re not immune, you’ll be advised to be particularly careful about possible exposure to the disease, because of the high risk to your baby if you contract rubella in your first trimester.
•    Haemoglobin (iron) levels: This shows whether your iron levels are okay. If you aren’t getting enough iron, you could have anaemia. Your iron levels are usually tested again at the start of your third trimester.
•    Hepatitis B: You can carry the virus without knowing it, and it can pass to your baby through the placenta, causing serious liver damage after birth. If you have an infection during pregnancy, your baby will be treated after birth to protect his liver.
•    Syphilis: It’s easily treated, but if left untreated it can cause serious developmental abnormalities for your unborn baby.
•    HIV: Your carer needs your consent to carry out the test, so you can reject the test if you prefer. If you’re HIV positive, your antenatal care, birth and baby feeding can all be tailored to minimise the chances of you passing it on to your baby.


Test for toxoplasmosis

In the UK, you’re not routinely screened for toxoplasmosis immunity in pregnancy. If you think you’re at risk of an infection, you can ask your midwife for a blood test to be done when you have your booking in tests.
Toxoplasmosis is an infection that can be picked up from raw or undercooked meat, and the faeces of infected cats (that’s why you told to avoid changing the kitty litter during pregnancy). It’s a rare infection in pregnancy, but it’s potentially damaging to your unborn baby.

Double, triple, quadruple tests

Blood tests to screen for developmental abnormalities are offered around 16-18 weeks. These look at the levels of certain hormones and proteins in your blood, to give an indication of the risk of your baby having conditions such as spina bifida and Down’s syndrome.
These blood tests can’t tell if your baby definitely has an abnormality. They offer an indication of your level of risk. If you’re high risk, you’ll be offered an amniocentesis.
Double test: To screen for spina bifida, a blood test looks for high levels of alphafeto protein in the blood. This may also be an indicator for Down’s syndrome. This test is combined with at least one other test, for the hormone human chorionic gonadotrophin (HCG). Together, these tests give a better indication of the risk of your baby having Down’s syndrome.
Triple test: This is where the level of oestriol in your blood is also tested.
Quadruple test: If you’re at a very high risk of Down’s syndrome, a fourth test that looks at the amount of inhibin A in your blood will be taken at the same time.

Glucose tolerance test

The glucose tolerance test checks for gestational diabetes and is usually carried out because you’re either:
•    Considered at higher risk of developing the condition, perhaps due to your age or weight
•    A routine urine test has shown there’s glucose in your urine

You need to have no food or drink (except than water) for 6 hours before the first blood test. This first blood test measures the level of sugar in your blood when you haven’t eaten. You’re then given a very sweet drink, and other blood tests are taken at intervals to see how your blood sugar level changes. This test can take several hours – take along a book or MP3 player and headphones for the waiting room.


Mums’ stories:

“He’s a lovely boy”

“After having the double test I was told that the results, combined with my age, indicated my baby had a one in 98 chance of having Down’s syndrome. I then had an amniocentesis, which confirmed that my baby did indeed have Down’s. I knew that I couldn’t go through with a termination, so I went ahead with the pregnancy. My older children supported me, and Joe is a lovely little boy.”
Bethany, 39, mum to Robert, 16, Lily, 8, and Joe, 3

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