Routine Prepregnancy / Early Pregnancy Laboratory Tests

Written by

Rob Buist

Published on


For many years now we – usually your GP – have conducted a number of lab tests as soon as you are pregnant or, preferably, even before you are pregnant.

Why do these tests before pregnancy?

Simple. This gives us an opportunity to address any potential problems that might crop up as a result of these tests. These can be simple – such as organising a vaccine for Rubella or Chickenpox – or more complex – managing Hepatitis B or C, for instance.

OK so what are these tests?

I’m going to divide these into two groups – those which are regarded as routine or standard, and those that I recommend in addition to the usual tests. Some of these are controversial.


  1. A Full Blood Count (FBC). This in essence assesses the amount of red stuff in your blood (haemoglobin) and the number of small sticky blood tests that help with blood clotting (platelets) amongst other things.
  2. Your iron level, or ferritin.
  3. Your blood group. We have two major blood group types – A, B or O (or AB), and Rhesus (Rh) Positive or Negative. Your Rhesus status is important – if you are blood group Rh negative there can be implications for all of your pregnancies. These are easily managed and are, well, the topic of another booklet.
  4. Your Rubella (German measles) immunity. Rubella can cause significant fetal abnormalities if you catch it during the first trimester. In countries like Australia most girls are immunised against Rubella at high school – so it is very rare – but nonetheless it is important to check.
  5. Your Hepatitis B status. If you have Hep B we can give your baby some Immunoglobulin (Ig) at birth to significantly reduce the risk of your baby catching Hepatitis B.
  6. Hepatitis C. If you have Hep C we may need to do some planning around the birth to reduce the risk of your baby being exposed to this virus.
  7. Syphilis. Don’t laugh; we do see it from time to time.
  8. HIV. Enough said.
  9. Varicella (or Chickenpox) immunity. Most of us have had Chickenpox or have been immunised so this is rare but it’s really important. If you aren’t immune to Varicella we can give you Varicella Ig if you’re exposed to this virus during pregnancy in order to prevent problems for yourself or your baby.  
  10. A urine sample, preferably a Mid-Stream Urine (MSU). It’s really helpful to find out if you have a urine infection (UTI) early in pregnancy so we can treat it and prevent a kidney infection. In addition a MSU can rule out a number of chronic kidney diseases.


  1. Your TSH (Thyroid Stimulating Hormone). Some women suffer from an underactive thyroid without any symptoms (Subclinical Hypothyroidism) and this can possibly cause problems for your baby if unrecognised and untreated. Subclinical Hypothyroidism is easily managed. 
  2. Vitamin D3. To be fair we are not entirely sure of the role – if any – of Vitamin D deficiency in pregnancy but most authorities recommend checking Vitamin D3 levels in women with dark skin. Being me, I check it on everyone.
  3. Your immunity to – or at least previous exposure to – three viruses that can harm your baby if you catch them during pregnancy. These are:
    1. Parvovirus B19, also known as Slapped Cheek. This virus can rarely cause fetal anaemia in pregnancy – and it’s a common infection in kids – so it’s useful to know if you’re immune to it or not.
    2. Toxoplasma (Toxo). Actually Toxo is not a virus, but a protozoan, but who cares? This is the infection that cats carry but you tend to get it from undercooked meat. Acquiring toxo in the first trimester is rare but it can cause fetal anomalies if you do.
    3. Cytomegalovirus or CMV. Catching CMV in early pregnancy can result in fetal abnormalities. CMV is a very common infection in young children so those of you with young kids – or who work with them – need to be particularly careful about not sharing body fluids with kids (I used to finish my kids’ chicken nuggets – healthy nutrition for sure – but that’s a bad idea if you’re pregnant). CMV is one of the more controversial blood tests for one reason. All of the other viral tests I have mentioned above are simple – if they indicate you are immune to them then you are immune – at least for the duration of the pregnancy – full stop. CMV is different. You can have previously contracted this virus – with the blood tests to show so – but you can still get it again. This is why many authorities do not recommend routine testing for CMV in pregnancy.


There are a number of other tests that may be performed depending on your ethnicity, family history or previous medical history. One such example – there are many – is testing for Thalassaemia by doing a blood test called a Haemoglobin Electrophoresis. This test is particularly important in women with Mediterranean (Greek, Italian, North African) or South East Asian backgrounds. 

Ashkanazi Jews who marry each other are at risk of giving birth to children with a number of what we call Autosomal Recessive conditions, including Tay Sachs Disease. At least one member of the couple should be tested for what we call their carrier status for these conditions (I will explain autosomal recessive inheritance elsewhere. One day). Most Australian Jewish high schools organise such testing on all of their pupils but it is worth making sure this has indeed occurred.  

What do I NOT routinely test for?

While I never say never (as James Bond said) and never say always, I tend not to test for the following things (unless there is a specific reason for doing so):

  1. Viruses or other infections that don’t harm unborn or newborn babies. Measles and Mumps are such examples.
  2. Minerals such as Calcium, Magnesium, Iodine and Zinc. If you don’t have a specific problem such as a gut absorption problem these tests will be normal – even if you are deficient in them (go figure). One off urine testing for iodine levels was popular a few years ago but is definitely not useful as it only tells us how much iodine you have consumed in the previous day or so.
  3. Vitamin B12 and folate levels. Again, unless you have a specific predisposition, these are going to be normal.