Routine Blood Tests in Pregnancy
At your first antenatal visit, a medical and surgical history will be obtained to see whether or not you have any particular medical condition which needs to be addressed in pregnancy. There will also be an assessment of your gestational age and estimated date of confinement as blood tests and ultrasounds need to be timed so that they are carried out at the optimum time during the pregnancy. Usually your initial blood test assessments will be carried out at around 10 weeks’ gestation as this is the appropriate time for genetic testing of the fetus which will be discussed on another blog. The routine blood investigations performed at this first antenatal visit include:
- Full blood examination: This is a test of your haemoglobin to exclude anaemia and also by measuring the size of the red blood cells (MCV) it is a test for a genetic blood disorder called Thalassemia. If Thalassemia is suspected, a more specific test will need to be carried out.
- Blood group and antibody screen: This is carried out in all pregnant women to ensure you are not Rh negative which will mean that you will require an injection of plasma anti D to prevent anaemia occurring in both this and subsequent pregnancies, if your partner is found to be Rh positive.
- Rubella antibody status: The majority of pregnant women have already had this tested and are Rubella immune. If you are found to not be Rubella immune you obviously should avoid contact with anyone with proven Rubella and should be re-immunised following the pregnancy.
- Syphilis serology: This is very rarely positive but is a recommended routine test so that appropriate treatment can be given to protect the fetus.
- Mid-stream urine: This is to identify any silent infection or any previously undiagnosed kidney disease.
- HIV: This is to exclude this virus in pregnancy so that treatment can be given to limit the chance of transfer of the virus to the fetus during the pregnancy.
- Hepatitis B serology: If pregnant women are found to be hepatitis B carriers it is possible to assess the quantity of virus in their blood stream which allows preventive treatment to avoid transfer of the virus to the fetus.
- Hepatitis C serology: Again this is unlikely to be positive, but allows us to take certain precautions to prevent transfer of the virus to other health care professionals especially.
- Varicella serology: Most pregnancy women are immune to chicken pox but precautions can be taken during the pregnancy if there is contact with a person having chicken pox, and it is recommended that we immunise pregnant women after their pregnancy if they are not immune.
- Ferritin levels: This is a measure of the stores of iron in your blood stream and gives us an idea whether or not you require further iron supplementation.
- Vitamin D levels: Again this tells us whether or not you need to be given additional vitamin D supplementation during the pregnancy.
- TSH levels: TSH is a thyroid function test and is primarily taken to ensure you don’t have an under active thyroid gland which may need to be treated during the pregnancy
- Routine pap smears: If you are due for a routine pap smear there is no reason why it can’t be performed early in pregnancy. There is no specific reason for undertaking a pap smear during pregnancy.
- CMV serology: CMV serology is not recommended as a routine test by the Royal Australian and New Zealand College of Obstetricians and Gynaecologists.
- Toxoplasmosis serology: Again this is not recommended as a routine test in pregnancy especially as toxoplasmosis is very rarely a problem in Australia
These tests are all carried out at one of the first antenatal visits, usually at about 10 weeks’ gestation. Screening for diabetes is ideally carried out at 28 weeks’ gestation and at this time thyroid function, full blood count, serum ferritin, vitamin D levels and blood group antibodies are all repeated to ensure that they are all normal heading in to the third trimester of pregnancy. You may be deemed to be high risk for having gestational diabetes either because of maternal age, family history, diabetes in a previous pregnancy, or some other risk factor. If that is the case then diabetic screening will also be undertaken early in the second trimester of pregnancy but will be repeated again 28 weeks if the initial test is normal.
Dr Len Kliman is one of Melbourne’s most experienced Obstetricians and Gynaecologists. With over three decades of experience, Dr Kliman has delivered over 20,000 babies and still counting!
In 2017, Dr Kliman was awarded an Order of Australia for his services to Obstetrics and Gynaecology.