Blood Tests at 28 Weeks: What to Expect and Why They Matter
Updated: Apr 10
As you approach 28 weeks of pregnancy, there are a couple of routine checks that are usually recommended around this time.
One of these is a set of repeat blood tests. These help build a clearer picture of how your body is supporting your pregnancy, and whether any additional support might be helpful.
What Blood Tests Are Done at 28 Weeks?
At this stage, we usually repeat a full blood count (FBC) and an antibody screen.
Some women will also be offered a test to assess their glucose levels.
Full Blood Count (FBC)
A full blood count looks at several important aspects of your blood, including:
Haemoglobin levels – which help assess for anaemia
Platelet levels – which play a role in your blood’s clotting system
This test gives a broad overview of your health and can highlight anything that may need a little more attention.
Antibody Screen
The antibody screen checks whether your body has developed any antibodies that could potentially affect your baby.
In most pregnancies, this test comes back completely normal, but it remains an important part of routine care to ensure everything is progressing safely.
Looking More Closely at Anaemia
If you’ve been experiencing symptoms that could suggest anaemia, a more detailed blood test may sometimes be recommended. This might include checking:
Ferritin – which reflects your iron stores
Vitamin B12 (and sometimes other nutrients)
This helps us understand why anaemia might be present, so that any treatment can be tailored appropriately.
If you’ve been experiencing symptoms that could suggest anaemia, a more detailed blood test may sometimes be recommended.
Symptoms of anaemia in Pregnancy
Anaemia can sometimes develop during pregnancy, and symptoms may include:
Feeling unusually tired or low in energy
Shortness of breath
Dizziness or feeling light-headed
Heart palpitations
Looking pale
It’s worth remembering that some level of tiredness is very normal in pregnancy. However, if these symptoms feel more pronounced or different from what you’d expect, it’s helpful to mention this so we can explore it further.
Gestational diabetes and the Oral Glucose Tolerance Test (OGTT)
Around this stage in pregnancy, you may also hear about testing for gestational diabetes (GDM).
What is Gestational Diabetes?
Gestational diabetes is a condition where blood sugar levels become higher than normal during pregnancy. This happens because pregnancy hormones can make it harder for your body to use insulin effectively.
In many cases, it does not cause obvious symptoms, which is why testing is offered to those who may be at higher risk.
What is the OGTT?
The oral glucose tolerance test (OGTT) is used to diagnose gestational diabetes. It usually involves:
A fasting blood test in the morning
Drinking a glucose solution
Further blood tests taken over the following 2 hours
Fasting usually means no food from 10pm the night before, but you can still drink water.
This allows us to see how your body processes sugar over time.
Who is Offered the OGTT?
In the UK, the OGTT is not offered to everyone routinely. It is usually recommended if you have certain risk factors, such as:
A previous history of gestational diabetes
A family history of diabetes
A higher body mass index (BMI)
Previous baby weighing 4.5kg or more
Certain ethnic backgrounds associated with higher risk
Your care team will discuss this with you if testing is recommended.
Why Is Testing Recommended?
The aim of identifying gestational diabetes is to:
Monitor blood sugar levels
Offer dietary and lifestyle support
Reduce the likelihood of complications such as a larger baby or birth interventions
A Balanced Perspective
Gestational diabetes has been widely screened for and managed for many years, with the aim of improving outcomes for both mother and baby.
However, the evidence shows a more nuanced picture. Research suggests that treatment of gestational diabetes can reduce the likelihood of certain outcomes, such as babies being larger than expected at birth and shoulder dystocia.
At the same time, the impact on other outcomes — such as perinatal mortality — is less clear, particularly in cases where blood sugar levels are only mildly elevated.
There is also ongoing discussion about:
The thresholds used to diagnose gestational diabetes
The increasing number of women being labelled with the condition
The potential for increased monitoring and intervention as a result of diagnosis
For some women, identifying and managing raised blood sugar levels will be beneficial. For others — particularly those with borderline results — the benefits of diagnosis and treatment may be less clear-cut.
This is why it’s important that decisions around testing and treatment are made on an individual basis, with a clear understanding of both potential benefits and wider implications.
If you are offered testing, it is always reasonable to ask:
What level of risk applies to me specifically?
What difference would treatment make in my situation?
What are my options moving forward?
Gestational diabetes has been widely screened for..with the aim of improving outcomes for both mother and baby. However, the evidence shows a more nuanced picture...
Making an Informed Decision
Like many aspects of pregnancy care, screening tests are your choice. Having clear, balanced information can help you decide what feels right for you.
If you’d like to talk this through in more detail, we can always explore your individual situation together.
A Reassuring Note
In most cases, these tests come back within normal ranges.
If anything does come up, it’s usually something that can be managed simply and effectively with the right support.
When to Reach Out
If you’re experiencing symptoms such as significant fatigue, dizziness, or shortness of breath, it’s always worth mentioning this — even if you’re not sure whether it’s “just pregnancy.” You don’t need to wait for your next appointment if something feels off.
You don’t need to wait for your next appointment if something feels off.
References and Further Reading
Pavord, S et al. (2019). UK guidelines on the management of iron deficiency in pregnancy
Regan, F et al. (2025). Guideline for the investigation and management of red cell antibodies in pregnancy.
Hillier, TA. et al. (2021). A Pragmatic, Randomized Clinical Trial of Gestational Diabetes Screening
Glasziou, P. and Doust, J. (2023). 1:6 Women are Diagnosed with Gestational Diabetes. But this Diagnosis may not Benefit them or their Babies
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