Diagnosing gestational diabetes

Diagnosing gestational diabetes

In this post we will be sharing risk factors and methods of diagnosing gestational diabetes in the UK and Ireland.

What is gestational diabetes?

Diabetes is caused by too much glucose (sugar) in the blood. The amount of glucose in the blood is controlled by a hormone called insulin.

During pregnancy, the body produces a number of hormones, such as oestrogen, progesterone and human placental lactogen (HPL). These hormones make the body insulin resistant, which means the cells respond less well to insulin and the level of glucose in the blood remains high.

To cope with the increased amount of glucose in the blood, the body should produce more insulin. However, some women either cannot produce enough insulin in pregnancy to transport the glucose into the cells, or their body cells are more resistant to insulin. This is known as 'gestational diabetes mellitus'. Gestational diabetes can be defined as carbohydrate intolerance.

insulin requirements during pregnancy
Fig 1. Marcinkevage, J.A., & Narayan, K.M. (2011). Gestational diabetes mellitus: taking it to heart. Primary care diabetes, 5 2, 81-8

Gestational diabetes is usually diagnosed by having a OGTT/GTT (oral glucose tolerance test) between 24 - 28 weeks, however women showing symptoms or those that have higher risks of developing gestational diabetes may be tested earlier.

Gestational diabetes affects around 5% of UK pregnancies


Are some women at a higher risk of getting gestational diabetes than others?

 You have an increased risk of gestational diabetes if:
  • your body mass index (BMI) is 30 or more
  • you have previously had a baby who weighed 4.5kg (10lbs) or more at birth
  • you had gestational diabetes in a previous pregnancy
  • you have PCOS (poly cystic ovarian syndrome)
  • you have a family history of diabetes – one of your parents or siblings has diabetes
  • your family origins are South Asian, black Caribbean or Middle Eastern
  • you are aged 35 or older


Risk factors for diagnosing gestational diabetes

Obesity is mentioned in the media a lot with regards to gestational diabetes and there is a stigma attached to GD diagnosis that only obese or unhealthy women get diagnosed. Sadly this means that many women feel it is not necessary to be tested because they are not overweight, or those that are diagnosed feel embarrassed or ashamed that they have caused this complication.

We see so many ladies joining our Facebook support group that are not overweight so we wanted to conduct some research from our members around risk factors linked to diagnosing gestational diabetes.

On a google survey that was advertised in our Facebook groups and our Facebook page (March 2018), we received 1,878 responses and here are the results:

When asked to select which of the following risk factors our ladies had, this is what we have found :

  • BMI (body mass index) of 30 or more 48%
  • Family history of diabetes 44.8%
  • Aged 35 or over 35.6%
  • Had gestational diabetes in a previous pregnancy 24.3%
  • Has PCOS (Polycystic ovarian syndrome) 15.5%
  • Previously given birth to a baby who weighed 10lb or more 6.8%
  • Family origins are South Asian, black Caribbean or Middle Eastern 4.2%
  • Pregnant with a multiple birth 1.5%


Obesity as a risk factor for gestational diabetes

Helen at 35 weeks pregnant

Obesity was found to be the biggest risk factor (48%) for gestational diabetes but does not mean you will definitely get gestational diabetes if you are obese. Obesity is the only risk factor that can be impacted by the mother before pregnancy. The rest of the risk factors are genetic or simply cannot be helped and so it could be for this reason that we see so much press around obesity and gestational diabetes risk.

It should also be noted, that although a BMI of 30 or more was the biggest risk factor found in our survey of 1,878 women, over half (52%, 977 women) did NOT have a BMI of 30 or more.

In this photo you can see Helen at 35 weeks pregnant who often had people commenting how could she have gestational diabetes being so slim, even medical professionals! One consultant said "I don't understand why you were tested, you don't look like you would have GD".

Sadly Helen is just one of many who has experienced these kind of comments and confusion. If we have medical professionals with this sort of opinion and presumption then no wonder we are faced with such challenges over gestational diabetes diagnosis.


No risk factors for gestational diabetes

How many women could be going undiagnosed and suffering the consequences of gestational diabetes if we have seen a result of almost 10% of women having none of the noted risk factors? This figure could in reality be much higher as these women are simply not getting screened because in many areas, only women with the above risk factors are screened.

It is often the case that we see women being screened in future pregnancies following the birth of previous large baby, or following a birth which was complicated with shoulder dystocia. On reflection, most of the women we see coming to our support group in these future pregnancies very often comment that they feel their previous pregnancy was undiagnosed GD.

It is for this reason that we believe that all pregnant women should be screened for gestational diabetes, not just the higher risk groups! This is something that is done in Cambridgeshire and if they can do it successfully, then they can do it everywhere!

Please help us raise awareness of gestational diabetes and encourage all pregnant women to be screened and at risk women screened earlier by sharing this page.


Reducing the risk of gestational diabetes

Recent research has shown that diet and exercise in those that have a high BMI before pregnancy, could reduce the risks of developing gestational diabetes and a further article published in BJOG stated:

Analysis of 13 trials, involving more than 2,800 women, found that exercise reduced the risk of gestational diabetes by more than 30% - for women who exercised throughout pregnancy this was even greater (36%). This effect was strongest for women who combined toning, strength, flexibility and aerobic exercise.


Symptoms of gestational diabetes

It is very common for no symptoms to be present and this is why many ladies feel that they can't possibly have gestational diabetes after receiving a positive result and struggle to come to terms with the diagnosis.

Some women may experience some symptoms such as:

  • Headaches
  • Blurred vision
  • Feeling thirsty
  • Feeling shaky or unsteady
  • Nauseous when needing to eat
  • Urinating more frequently
  • Tiredness
  • Recurrent infections, such as urinary tract infections (UTIs) and thrush

You will notice that many of these symptoms are common during a normal pregnancy and so it is hard to determine if they are due to gestational diabetes or just pregnancy itself until a glucose tolerance test is performed.

If you have any of the above symptoms you should enquire about being tested for gestational diabetes.


Diagnosing gestational diabetes in the UK and ROI

For women with any of the above risk factors, a 2 hour 75 g oral glucose tolerance test (OGTT or GTT) is used to for diagnosing gestational diabetes between 24 - 28 weeks.

If glycosuria (glucose in urine) of 2+ or above on 1 occasion, or of 1+ or above on 2 or more occasions is detected by urine dip test during routine antenatal appointments, this may  indicate undiagnosed gestational diabetes and so women with this should be referred for an OGTT.

In some areas all pregnant women are screened for gestational diabetes.

Those that have previously been diagnosed with gestational diabetes are often tested at 16 weeks in subsequent pregnancies and again at 24 - 28 weeks should the first test come back as negative.  Some hospitals will not test for gestational diabetes in subsequent pregnancies and may offer blood glucose monitoring from an early gestation instead.


 What is an Oral Glucose Tolerance Test (OGTT or GTT)?

This is the test used for diagnosing gestational diabetes in the UK & ROI.

Blood test OGTTThe test involves fasting (not eating or drinking) from the previous night, having a fasting blood test taken on arrival, drinking 75g of glucose (this may be in the form of a glucose syrup drink), then a subsequent post glucose blood test taken after 2 hours.

You should check with your hospital when you should fast from and whether you are allowed to drink water during this time.

All hospitals can vary the targets used for diagnosis of the OGTT.  Some will take three blood tests (fasting, one hour and two hours post glucose), where as others will take two (fasting and one hour post glucose).

In some areas they may use a fasting glucose test alone or a HbA1c blood test instead of a OGTT.


Diagnosis test target levels England & Wales:

NICE guidelines (recommendations for England & Wales) for diagnosis are the following:

1.2.8 Diagnose gestational diabetes if the woman has either:

  • a fasting plasma glucose level of 5.6 mmol/litre or above or
  • a 2‑hour plasma glucose level of 7.8 mmol/litre or above. [new 2015]


Diagnosis test target levels Scotland:

SIGN guidelines (recommendations for Scotland) for diagnosis are the following:

  • The adoption of internationally agreed criteria for gestational diabetes using 75 g OGTT is recommended: ƒ fasting venous plasma glucose ≥5.1 mmol/l, or ƒ one hour value ≥10 mmol/l, or ƒ two hours after OGTT ≥8.5 mmol/l.
  • Women with frank diabetes by non-pregnant criteria (fasting venous glucose ≥7 mmol/l, two hour ≥11.1 mmol/l) should be managed within a multidisciplinary clinic as they may have type 1 or type 2 diabetes and be at risk of pregnancy outcomes similar to those of women with pre-gestational diabetes.
Diagnosis test target levels Ireland:

HSE guidelines (recommendations for Ireland) for diagnosis are the following:

A diagnosis of gestational diabetes is made when one or more values are met or exceeded

  • Fasting 5.1mmol/L
  • 1 hour 10.0mmol/L
  • 2 hour 8.5mmol/L


Borderline diagnosis

Borderline diagnosis can have very different meanings when it comes to gestational diabetes. It could mean that following your GTT your fasting or post glucose levels were:

  1. Just below the threshold targets
  2. Bang on the threshold targets
  3. Just over the threshold targets

Bearing in mind that test threshold target levels differ from one hospital to another, this could be a huge difference in actual blood glucose levels and therefore what is classed as borderline in one hospital may be a clear positive test result in another.

We feel that if you have been told to monitor your blood glucose levels, then you will benefit from modifying your diet to a GD friendly one, such as our 8 golden rules.

With gestational diabetes being a progressive condition, it is very common for borderline diagnosed women to have increased insulin resistance further into the pregnancy and many in fact, end up requiring medication to help control their levels, despite being 'borderline' on their initial test. For more information on borderline diagnosis and personal experiences after being told they have 'borderline' results, please read more here.


Is my baby at risk if I have gestational diabetes?

When blood glucose levels are poorly controlled then additional sugar is passed through to the baby, as a result the baby can grow to be large for gestational age. This in turn can cause problem for both the baby and the mother during birth and then for the baby post birth. Contrary to belief, gestational diabetes does not just cause bigger babies.  In fact, when gestational diabetes is diagnosed and managed well, it is rare for babies to be 'big'.

Most women with gestational diabetes go on to have normal pregnancies with healthy babies, but there are many complications associated with the condition, some which can be very serious. 

**The risk of complications is greatly reduced if gestational diabetes is diagnosed and managed properly throughout your pregnancy**

If you would like to see some of the complications caused by and related to gestational diabetes then please read more here.


What to do once diagnosed?

By reading the information on our website and joining our Facebook support group, we can help support you with how best to lower and stabilise blood sugar levels and ultimately help you manage the condition. From diagnosis to post birth testing, we have all aspects of information covered to help you make informed choices and learn more based on what we've learnt through previous members and thorough research.



warning2Controversy surrounding the oral glucose tolerance test for diagnosing gestational diabetes

There is controversy surrounding the GTT due to two things:
  1. The drink given to take the test
  2. The amount of glucose given v's the lack of exercise to help process the glucose during the test


1. The glucose drink used for diagnosis in the UK and ROI

Last year Lucozade changed the amount of glucose in their drink to help lower the amount of sugar consumers are drinking, therefore to deliver a 75g glucose load would require in excess of 800mL of Lucozade! For this reason, the majority of hospitals will now be using a glucose replacement drink to conduct the OGTT.

glucola not used in the UKYou may see pictures of a glucose drink (Glucola) which is used in the USA for gestational diabetes testing and pictures of babies in the womb with slogans like "Mom, don't drink the glucola" or "don't drink this toxic drink". The problem with Glucola is BVO, or brominated vegetable oil (a product that keeps the favouring from floating to the top of the drink) and it is found in many US drinks. Brominated vegetable oil is banned as a food additive in Europe under Regulation (EC) No 1333/2008.

Please note, this is NOT the same as the products used in the UK! In the UK and Ireland there are a few different glucose load options used:

Gestational Diabetes OGTT Polycal drinkPolycal:

  • Ingredients (Neutral) Demineralised water, glucose syrup, maltodextrin, acidity regulator (citric acid).
  • Ingredients (Orange) Demineralised water, glucose syrup, maltodextrin, acidity regulator (citric acid), flavour (orange), colour (curcumin, anthocyanins)

Rapilose: Ingredients Water, glucose syrup, glucose monohydrate, flavouring, citric acid (acidity regulator), potassium sorbate, sodium benzoate (preservatives)

Glucose monohydrate/ Glucose BP/ Dextrose monohydrate (dextrose powder)

If you have any concerns over the product used for diagnosing gestational diabetes, then you could ask to see the listed ingredients before taking the test.

For those who are reluctant to take a test which is based on the glucose drink,  you could ask if your health care professionals would consider testing with a specific high carbohydrate load breakfast, although this is something that is only allowed in exceptional circumstances and is no longer common practice.


2. Lack of activity following the high glucose load

With regards to not being allowed to be active between drinking the glucose and having further blood tests, at Gestational Diabetes UK we feel that if your pancreas is producing and using enough insulin i.e. non-diabetic, then your body will be able to process the glucose enough to show a negative result.

NICE test targets have been questioned recently as to whether they are too low and missing around 4,000 cases of gestational diabetes per year.  This is shown by the University of Cambridge, "New NICE thresholds could miss up to 4,000 women per year at risk from diabetes in pregnancy" - To read this research see more here.


Is there another way to test without taking the GTT?

If you feel strongly that you do not want a GTT for diagnosing gestational diabetes, then you should discuss your reasons with your health care professionals.

Many hospitals will happily agree to home blood glucose monitoring which involves testing blood sugar levels at home with a blood glucose monitor and test strips.


Should I avoid or decline being tested?

Ultimately it is up to each mother to make an informed choice as to what is best to do for her baby and pregnancy.

You cannot be forced into testing, but we highly advise looking at the complications gestational diabetes can have on your baby and you, many of which are symptomless.

Monitoring blood sugar levels to record findings after all meals would be a beneficial step, should you choose to refuse a GTT and is ultimately the most important thing in helping to manage the condition.

Refusing BOTH the GTT and monitoring blood sugar levels at home, could lead to many complications for your baby should you have undiagnosed and uncontrolled blood sugar levels.


"Gestational diabetes just causes a bigger baby..."

Anyone who is under the assumption that gestational diabetes will 'just cause a bigger baby' and that is the only risk factor, should learn about the associated complications. Please read more here on the complications caused by gestational diabetes.

Gestational Diabetes UK is dedicated to offering support and evidence based research to women diagnosed with gestational diabetes in the UK and Republic of Ireland.

Gestational Diabetes UK Facebook groupIf you have been diagnosed, or are going to be tested for gestational diabetes and want a support network and community for help, advice and to discuss all things related to gestational diabetes, then please join our Facebook support group, Gestational Diabetes UK Mums.



 UK and ROI guidelines:-

NICE guidelines ng3 Diabetes in pregnancy: management of diabetes and its complications from preconception to the postnatal period

SIGN guidelines 116 Management of diabetes: A national clinical guideline

HSE Guidelines for the Management of Pre-gestational and Gestational Diabetes Mellitus from Pre-conception to the Postnatal period