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Gestational Diabetes

Updated: Nov 30, 2023

Hello mummies / future mums

Let's delve into the world of Gestational Diabetes

Gestational diabetes or GDM is characterised by elevated glucose levels that are initially identified during pregnancy, typically around 26-28 weeks. It is surprisingly common affecting 1 in7 women in the UK.

Who can develop gestational diabetes?

GDM does not discriminate but certain factors increase the likelihood of it developing such as

- Being over 40 years of age

- BMI over 30

- Specific ethnicities (being of South Asian, African-Caribbean origin)

- Family history of diabetes

- Previous pregnancy with GDM

- Previous baby weighing 10lbs (4.5kg) or over

Although there are a number of risk factors as above, I have seen many women in my clinics without any risk factors too. Women with one or more or these will be offered a glucose tolerance test to check for gestational diabetes.

How is it diagnosed?

A glucose tolerance test is where the blood glucose is checked on fasting, followed by consuming a 75g glucose drink and then another blood test 2 hours after the drink.

GDM is diagnosed if the fasting blood glucose reading is 5.6mmol or above and or the two-hour glucose is 7.8mmol or above. In some cases a HbA1c blood test is used to diagnose GDM rather than a glucose tolerance test.

Why does gestational diabetes happen?

Raised glucose levels in GDM are a result of the hormone insulin not being able to maintain glucose levels within a tight range. Insulin is usually produced in order to use glucose as energy or to be stored in our cells. The newly formed organ, the placenta produces several hormones including progesterone and oestrogen. The significant rise in these hormones results in insulin resistance. Insulin resistance is a process where the body is producing insulin but it may not be utilised efficiently and therefore glucose levels rise. Insulin resistance in pregnancy is a normal phenomenon and thought to occur as an adaptation to ensure a sufficient supply of carbohydrate to the rapidly growing baby!

In women who do not have GDM the pancreas beta cells will produce more insulin to meet the demand and keep glucose levels optimal, however those who are not able to keep up with the extra demand of insulin go on to develop GDM.

What are the risks associated with GDM?

- Macrosomia (Large baby over 4000g)

- Shoulder dystocia

- Premature birth (birth before 37 weeks)

- Baby develop hypoglycaemia (low glucose) or jaundice after birth which may require extra medical attention

- In rare cases miscarriage or still birth

- Polyhydramnios – excess amniotic fluid

- Pre-eclampsia

- Mother and baby have high risk of future diagnosis of Type 2 Diabetes

- Mother to have higher risk of GDM in subsequent pregnancies

Due to the above risks some women may be advised to have an induction or c-section before their due date. NICE guidance otherwise states to “advise women with uncomplicated gestational diabetes to give birth no later than 40 weeks plus 6 days. Offer elective birth by induced labour or (if indicated) by caesarean women to women who have not given birth by this time”.

To reduce these risks women are given target glucose levels and asked to check their blood glucose on waking (fasting) and also 1 hour after meals.

These targets vary across the country but NICE targets are:

Fasting <5.3mmik

1 hour post meal <7.8mmol

What is the treatment?

First line treatment is diet and lifestyle changes. This involves following a low glycaemic index diet, being mindful of carbohydrate potions and including regular exercise. For 1/3 women despite these changes, they may still need oral medications or insulin to keep glucose levels in target.

Example meal plan for gestational diabetes

Breakfast: 1-2 slices of seeded bread with 2 poached eggs, ½ avocado and mushrooms

Mid morning: Greek yoghurt with 5 strawberries and almonds, walnuts

Lunch: ½ plate quinoa, salmon and ½ plate side salad

Mid afternoon: 1-2 oat crackers with cream cheese, vegetable crudites

Dinner: ¼ plate brown basmati rice with stir fry chicken/tofu, broccoli, and peppers topped with sesame seeds

Evening/before bed snack: 1 medium apple with almond peanut butter

Understanding and managing GDM is a shared journey If you're nativigating this path, remember, you are not alone.

As a dedicated prenatal specialist dietitian who has worked in the diabetes space for several years, I have a passion for supporting women with GDM. Why not get in touch with me and embark on this journey together.


Plows JF, Stanley JL, Baker PN, Reynolds CM, Vickers MH. The Pathophysiology of Gestational Diabetes Mellitus. Int J Mol Sci. 2018 Oct 26;19(11):3342. doi: 10.3390/ijms19113342. PMID: 30373146; PMCID: PMC6274679.

Kampmann U, Knorr S, Fuglsang J, Ovesen P. Determinants of Maternal Insulin Resistance during Pregnancy: An Updated Overview. J Diabetes Res. 2019 Nov 19;2019:5320156. doi: 10.1155/2019/5320156. PMID: 31828161; PMCID: PMC6885766.

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