What is Gestational Diabetes?

Lets break it down!

Rebecca Newell

4/16/20244 min read

Gestational Diabetes affects around 5% of pregnancies in the UK (gestationaldiabetes.co.uk)

What is it?

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 several hormones, such as oestrogen, progesterone and human placental lactogen. 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. When this happens, blood glucose levels remain too high. This is known as ‘Gestational Diabetes Mellitus’. (gestationaldiabetes.co.uk)

The term Gestational Diabetes (GD) is used in the maternity system to identify and manage women with high blood glucose levels (BGL) during pregnancy. Most cases of GD are pregnancy-induced, resulting from an inability to meet the additional insulin needs of pregnancy. Occasionally, pre-existing Type 2 diabetes is identified during pregnancy, but high BGLs are labelled as GD until proven otherwise, such as when they persist after pregnancy.

In the UK everyone is offered a gestational diabetes. But (and this is a biggie), there is significant variability in the diagnosis and labelling of GD due to inconsistencies in testing criteria, screening approaches, and populations tested. SO the incidence of GD varies globally, ranging from 2% to 26%, depending on the definition used and the screening approach.

“… the diagnosis of gestational diabetes is not at all clear cut. The guidelines, tests and cut-off points used to decide whether a woman has gestational diabetes differ widely between countries and areas. This is incredibly confusing and unhelpful…” (Inducing Labour: making informed decisions -Wickham 2018).

Obesity is mentioned in the media a lot with regards to gestational diabetes which is shit for two reasons;

  1. There is a stigma attached to GD diagnosis that only obese or unhealthy women get diagnosed.

  2. Those that are diagnosed feel embarrassed or ashamed that they have caused this complication.

What are the risk factors linked to diagnosing gestational diabetes?

  • your body mass index (BMI) is 30 or more (we know BMI is bollocks, if you don’t have a google)

  • 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 (polycystic 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

In a survey conducted in the UK Gestational Diabetes Facebook Support Group which received 1878 responses, people diagnosed with GD selected their risk factors;

  • 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%

  • No risk factors above 9.8%

So how do we screen for it?

There are two main approaches to GD screening: universal screening (offered to all pregnant people) and risk factor-based screening (offered only to people at an increased risk of GD). Both approaches lack clear evidence for improving outcomes for mothers and babies.

Oral Glucose Tolerance Test (OGTT)

This is the standard universal test which is usually conducted between 24 and 28 weeks of gestation. It involves fasting overnight, drinking a glucose solution, and having blood tests to assess BGLs. The timing and dose of glucose can vary, but most guidelines recommend 75g of glucose and a 2-hour blood test. The OGTT evaluates a woman's response to a large dose of glucose.

Glycated hemoglobin Test

This is only recommended for identifying pre-existing diabetes in the first trimester and cannot effectively detect pregnancy-induced diabetes.

Self-testing is not recommended in official guidelines, although some women choose this method to monitor their BGLs over a few days.

A Cochrane Review concluded: There is not enough evidence to guide us on effects of screening for GDM based on different risk profiles or settings on outcomes for women and their babies… Low-quality evidence suggests universal screening compared with risk factor-based screening leads to more women being diagnosed with GDM.”

Can we treat Gestational Diabetes?

If you are diagnosed with GD you may find yourself being ushered into ‘GD-centred’ antenatal care. Not only, and as I mentioned above there is usually a stigma attached to having GD, but you may also find you will then also receive lots of extra medical attention you may or may not want.

NHS recommendations for managing GD focus on keeping BGL within a certain range. Meaning you may have to change your diet, do more physical activity, and sometimes take insulin. It's important to note that the diet often suggests eating a lot of carbohydrates (sugar).

As Sara Wickham points out “while there are some short-term benefits to people with GD who receive lifestyle interventions compared to people with GD who didn’t…it might be that these are beneficial to everyone.”

So does Gestational Diabetes affect me and my baby?

In a study done on the link between maternal blood sugar and risk of poor birth outcomes (HAPO, 2008) they found that the risk of poor outcomes increases with every small increase in blood sugar levels. they linked GDM to higher rates of;

  • Pre-eclampsia

  • Foetal high blood sugar

  • First-time Caesarean

  • Premature birth

  • Macrosomia

  • Shoulder dystocia or birth injury

  • Newborn intensive care

  • Newborn jaundice

  • Newborn low blood sugar

What’s super important to note is that some of these outcomes may be the result of advice or even coercion by medical professionals to medically induce you along with the possible snowball of sequential interventions.

You can see the evidence (or lack of) to support induction and the birth rights of an individual with gestational diabetes in my post 'I have to have an induction because I’ve got gestational diabetes'.

Now excuse me while I have a lie down.


The Midwives' Cauldron Katie James and Dr Rachel Reed (Podcast)

Dr Rachel Reed - Gestational Diabetes Beyond the Label (blog)

Inducing Labour: making informed decisions. - Sarah Wickham (book)

Gestational diabetes - sarawickham.com

Evidence on: Diagnosing Gestational Diabetes - evidencebasedbirth.com