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Blood tests are an integral part of antenatal care since they provide health professionals with important information about the health of both mother and baby. There are routine blood tests in pregnancy, which are part of the usual prenatal checks and screenings, and specialised blood tests that are used for screening for certain conditions.
What blood tests are done during pregnancy? What do they test for? How many blood tests are offered? What blood test is done for abnormalities in early pregnancy? Read the answers here.
Table of contents
What blood tests are done during pregnancy?
Routine blood tests in pregnancy
Special blood tests during pregnancy in the first trimester
Pregnancy blood tests used for screening for trisomies
Benefits of having blood tests in pregnancy
A final word on pregnancy blood tests
What blood tests are done during pregnancy?
During pregnancy, blood tests can be used for different purposes. Their specific purpose depends on when and why they are done. Here is an overview of different pregnancy blood tests:
- Blood test for determining blood group and rhesus status of both mother and baby
- Antenatal screening blood tests for trisomies 13, 18 and 21
- Screening for HIV, syphilis and hepatitis B infections
- Blood test for checking maternal iron levels in pregnancy
- Screening test for certain inherited conditions
- Pregnancy blood sugar test for detecting gestational diabetes
- Pregnancy test using blood instead of urine
Routine blood tests in pregnancy
Blood tests are part of the routine antenatal checks and screening tests. During a normal pregnancy, mums-to-be will have up to ten antenatal appointments with an obstetrician or midwife (sometimes also only seven if they have had a child before). At the booking appointment, the mother’s blood is tested for anaemia which is repeated during the appointment that takes place around week 28.
Good to know: Many expectant mothers wonder how many blood tests during pregnancy they’ll be offered. This depends on the treating doctor and also on the mother’s iron levels at the beginning of the pregnancy.
Other pregnancy blood tests include screening for gestational diabetes, HIV, hepatitis B, syphilis, testing for rhesus status of mother and baby and screening for chromosome disorders or inherited blood disorders.
Special blood tests during pregnancy in the first trimester
Many mums-to-be wonder what blood tests are done in the first trimester. There are several blood tests that should be done early on in pregnancy. Here is an overview.
- Screening for sickle cell disease (SCD) and thalassaemia before 10 weeks of pregnancy (screening for thalassaemia is offered to every pregnant woman, SCD screening is only offered to those at high risk of being a carrier)
- Screening blood tests for HIV, hepatitis B and syphilis (ideally by week 10)
- Screening for three different chromosome disorders between weeks 11 to 14 (together with the first ultrasound scan in pregnancy)
The screening blood tests for infectious diseases and inherited blood disorders deliver a definitive result regarding whether you have one of these conditions and whether you are a carrier. Screening tests for chromosome disorders, on the other hand, only indicate how high or low the risk is that your baby will be born with a condition.
Pregnancy blood tests used for screening for trisomies
All expectant mothers in the UK are offered a screening test for Down's syndrome (trisomy 21), Edwards' syndrome (trisomy 18) and Patau's syndrome (trisomy 13). One possible screening method is the combined test which is a combination of a blood test with an ultrasound scan that measures the baby’s nuchal translucency.
The results of both screening tests are then used to calculate the risk of the baby being born with a chromosomal disorder. The combined test is performed between the 10th and 14th week of pregnancy.
In cases where the combined test is unsuccessful, the quadruple blood test can be used as an alternative. The quadruple test is done at a later stage of pregnancy, typically between weeks 14 and 20. It is less accurate than the combined test and only scans for trisomy 21, aka Down’s syndrome.
If any of these tests indicate that there is a high chance that the baby will be born with a condition, further tests are needed for confirmation. This can either be another screening test or a diagnostic test.
Another screening blood test in pregnancy that can be used to investigate the chance of the baby having a trisomy 21, 18 or 13 is non-invasive prenatal testing (short: NIPT). NIPT results are more accurate than other screening tests for trisomies, but still don’t deliver a final diagnosis. For this, a diagnostic test is needed.
Prenatal diagnostic tests that can deliver definitive results on whether or not the baby will have a chromosome disorder include amniocentesis (amniotic fluid test) and chorionic villus sampling (removing and testing a small sample of cells from the placenta).
Benefits of having blood tests in pregnancy
Blood tests in pregnancy are an important part of antenatal care. The aim is to detect complications early on in pregnancy and screen for possible conditions in the baby. Among other things, antenatal blood tests can help:
- detect iron deficiency in pregnancy and increase maternal iron intake with supplements
- calculate the risk of the baby being born with a trisomy
- screen for certain inherited conditions
- prevent that maternal infections are passed on to the baby
- take certain precautions to reduce the risk of rhesus disease
How much does it cost to have blood tests in pregnancy?
Routine blood tests in pregnancy are offered to all expectant mothers. Since they are part of antenatal care, they are offered free of charge. This includes screening tests for conditions like Down's syndrome, blood tests for infectious diseases like HIV, blood tests for inherited diseases like thalassaemia and routine blood tests to check for gestational diabetes, iron deficiency anaemia and rhesus status. Whether or not further antenatal screening tests are offered depends on the likelihood of the baby being born with a condition.
A final word on pregnancy blood tests
Blood tests during pregnancy provide important information about the health of both mother and baby. In addition to blood tests that are part of regular maternity care, health professionals can do further tests to screen for certain conditions in the baby.
Here is a recap of the different pregnancy blood tests that are offered in the UK:
- Blood screening for anaemia
- Blood test to determine blood group and rhesus status
- Screening for infectious diseases (hepatitis B, HIV and syphilis)
- Blood test for gestational diabetes
- Screening for inherited conditions (namely sickle cell and thalassaemia)
- Combined blood test and ultrasound scan to screen for trisomies 13, 18 and 21
References
- Pregnancy blood and screening tests – are they necessary? | Pregnancy articles & support | NCT
- Screening tests in pregnancy - NHS (www.nhs.uk)
- Antenatal checks and tests - NHS (www.nhs.uk)
- Screening for hepatitis B, HIV and syphilis - NHS (www.nhs.uk)
- Screening for sickle cell and thalassaemia - NHS (www.nhs.uk)
- Screening for Down's syndrome, Edwards' syndrome and Patau's syndrome - NHS (www.nhs.uk)
- Screening tests for you and your baby (STFYAYB) - GOV.UK (www.gov.uk)
- Combined first-trimester screening — Knowledge Hub (hee.nhs.uk)
