What Exactly Is A Glucose Tolerance Test And What Is It For?
A glucose tolerance test (GTT or OGTT – Oral Glucose Tolerance Test) is done to check how your body handles sugar (glucose). It isn’t only a test for during pregnancy, but is can be done on anyone, to see how their body copes with breaking down sugar, and whether they have diabetes.
Why Am I Offered a GTT in Pregnancy and Why in Particular Because I Have a High BMI?
Just being pregnant makes it more likely you will develop diabetes compared with if you weren’t pregnant – due to the changes in your body that happen as pregnancy progresses. The formal name for pregnancy diabetes is gestational diabetes. In the vast majority of cases, gestational diabetes will go away again after your baby is born, but sometimes it doesn’t. Gestational diabetes Is when your pregnant body doesn’t produce enough insulin to process the sugar in your system.
Predicting who this will and won’t happen to in pregnancy is impossible, but there are some factors which mean the chances might be higher. One of these is if you are a plus size when you are pregnant. What is important to stress though is, the vast majority of ALL pregnant women will NOT develop diabetes
So What are the Facts and Figures? As a Plus Size Pregnant Woman, What’s My Chances… Exactly?
Nobody can tell you your exact risk of developing diabetes in pregnancy. You probably had your body mass index (BMI) calculated early in pregnancy. Put very broadly, across the whole UK population, around 4 in every 100 women with a BMI 19-25 (‘normal’ range – check my inverted commas!) will develop diabetes in pregnancy, while around 8-10 in every 100 plus size women (BMI 30+) will develop diabetes.
Hopefully you can see here that, the chances are a bit higher if you are plus size, but feel reassured that your most likely experience by far is that you will not develop diabetes.
Based on that increased chance though, your midwife or doctor might recommend you have a GTT at 26-28 weeks pregnant. This timing is because gestational diabetes develops most commonly after 20 weeks of pregnancy. Some pregnant women with other factors might be offered an earlier GTT. This might happen if some of your family member have diabetes, or if you’ve had gestational diabetes before, making it more likely you could develop it again, earlier than usual , or perhaps that it never quite went away after your last pregnancy.
So What Actually Is a GTT and How Do I Pass or Fail?
I do hear people talk about ‘passing’ a GTT, but it doesn’t really work like that. If you have a GTT, you’ll be asked to go along to the surgery or hospital early in the morning, having had no breakfast and nothing to drink (fasted) since the night before. Someone will take a blood sample from your arm and then you’ll be asked to drink a large serving of a sugary drink. This is usually Lucozade. You’ll then be asked to sit still somewhere (a waiting area usually) for around two hours (so bringing your fully charged phone, or a book or some work do is highly recommended). It is important to sit still and not go for a wander about as the test is more accurate if you don’t use any energy through walking about (preferably not even talking!), just sitting quietly and letting your body get to work processing that sugar. Once the two hours is up, someone will take another blood sample from your arm. The test process is then complete. You can go get breakfast!
What a GTT looks for is: First blood sample, how much sugar is in your system when you have eaten nothing for several hours (has your body sorted the sugar level out overnight, is it low and within normal range): Second blood sample: how has you body coped, over a couple of hours, with a big rush of sugar? Can it produce the insulin to process it in the expected way? The result, in particular of the second sample will tell if you have developed diabetes. If it is close to the limit for diabetes but is just under it, you may be asked to repeat the test a few weeks later.
So, the results aren’t so much a pass or fail, although obviously you may end up wit a diabetes diagnosis – and consider this a fail – but you shouldn’t If you get diabetes in pregnancy, it isn’t your ‘fault’, and the diagnosis is really important so you can get advice and treatment if you need it.
I’ve looked after many women with diabetes who cope with it very well and manage to maintain healthy blood sugar levels through acquiring the right knowledge, supportive care and following a plan made in partnership with sympathetic respectful care providers. So, my advice is to take the GTT, try not think of ‘pass’ or ‘fail’ – it’s there to help keep you and your baby safe. Do ask the questions that you need to and get in touch with me if you need help or support.
And whatever your GTT result, do read my Blog ‘Not so Short and Not So Sweet’ for my take on weight gain and dietary advice. Spoiler: my top tip is this… In Pregnancy, Sugar is Absolutely Your Enemy!