BLOG BY Elle Coales BSc MSc ANutr RYT

Gestational Diabetes: An Introduction

Gestational diabetes mellitus, or GDM, is a form of diabetes that affects pregnant people. According to the European Association for the Study of Diabetes (1), GDM is defined as any degree of glucose intolerance that is not clearly pre-existing diabetes. Having GDM can increase the risk of high blood glucose levels in your new-born, macrosomia (large for gestational age babies), needing a caesarean section and preeclampsia. Because of this, managing your gestational diabetes is important if you are of the 18% of people diagnosed with it.

Why do some people get GDM?

Due to changing hormone levels, insulin resistance increases in later pregnancy. Not everyone is able to compensate for this increase, which can lead to GDM. Pre-existing conditions such as PCOS, having macrosomia in a previous pregnancy, a family history of diabetes or being from certain ethnic backgrounds can increase your risk of GDM (2).

A study looking at preventing GDM had participants following healthy eating advice and aiming to exercise for 30 minutes for 5 days per week if they were either planning a pregnancy or less than 20 weeks pregnant (3). Results are still ongoing but suggest that these interventions may help to reduce the risk of developing GDM.

Getting diagnosed

Screening for GDM is a routine part of antenatal care, with an oral glucose tolerance test offered between 24-28 weeks to anyone with 1 or more GDM risk factors. This measures your blood glucose level after consuming a sugary drink to see if they follow a “normal” pattern or one that looks more like

Managing GDM

Lifestyle interventions including diet and exercise can help to manage blood glucose levels and improve insulin sensitivity. However, if this doesn’t work, medication may be necessary. Common medication includes oral metformin, or insulin therapy.

For exercise, guidelines recommend 30 minutes of moderate physical activity 5 times a week unless you’ve been advised not to for medical reasons. Regular exercise like this can reduce HbA1c levels (a proxy for average blood glucose levels). Just speak to your doctor or antenatal health team if you need to clarify what forms of exercise are safe.

There’s no one diet for GDM, but guidelines include favouring carbohydrates from wholegrains, legumes, fruits and vegetables over more simple carbohydrates. These more complex carbohydrates tend to be slower to digest and higher in fibre, helping to support keeping your blood glucose levels. In particular, being mindful of higher sugar foods can be helpful.

To help with managing GDM, your blood glucose levels will be checked regularly, either by self-monitoring or at check-ups. Weight gain is an expected part of pregnancy, but if your weight or BMI is at a higher-level pre-pregnancy, then you may be advised to aim for a smaller weight gain during pregnancy. This may help with insulin resistance and reduce the risk of a large for gestational age foetus, and the birth complications that are associated with larger babies. If this is a sensitive area for you, asking for weight measurements not to be visible to you, or focusing on behaviour change rather than weight goals may be an option to discuss with your healthcare provider.

Healthy labour and 4th trimester with GDM

If you have GDM, your healthcare provider will make personal recommendations for a safe labour, but it is likely that your glucose levels will be monitored throughout active labour. Your newborn’s glucose levels will also likely be checked.

Breastfeeding is associated with improved glucose levels both immediately and longer term for the mother (4), so is recommended where possible. As GDM increases the risk of developing type 2 diabetes, or GDM in later pregnancies (5, 6), continuing with some of the lifestyle recommendations can help to reduce this risk. If your blood glucose levels stay in the pre-diabetic range after pregnancy, you may be eligible for the NHS diabetes prevention programme for ongoing support.

Make sure you are signed off to exercise before you start with a new routine, but walking can be a great option for both your physical and mental health.

Being diagnosed with gestational diabetes isn’t something that can be completely eliminated through diet and exercise alone. However, these lifestyle measures may help to reduce your risk, and can help with the management and aftercare of GDM as well as your long-term health.

This post was written by Elle Coales, an Associate Registered Nutritionist and yoga teacher. Elle has a Master’s Degree in Nutrition from the University of Leeds and works as a Nutritionist on the National Diabetes Prevention Programme. She has a special interest in offering gentle nutrition support for women’s health including PCOS, fertility, pre/post natal and the menopause. She also works as a social media intern for Forking Wellness and Dietitian UK. You can find Elle on Instagram @enliveningelle


1. American Diabetes Association, 2019. 2. Classification and diagnosis of diabetes: standards of medical care in diabetes—2019. Diabetes care42(Supplement 1), pp.S13-S28.

2. Buchanan, T.A., Xiang, A.H. and Page, K.A., 2012. Gestational diabetes mellitus: risks and management during and after pregnancy. Nature Reviews Endocrinology8(11), pp.639-649.

3. Rönö, K., Stach-Lempinen, B., Klemetti, M.M., Kaaja, R.J., Pöyhönen-Alho, M., Eriksson, J.G. and Koivusalo, S.B., 2014. Prevention of gestational diabetes through lifestyle intervention: study design and methods of a Finnish randomized controlled multicenter trial (RADIEL). BMC pregnancy and childbirth14(1), pp.1-11.

4. Gunderson, E.P., 2007. Breastfeeding after gestational diabetes pregnancy: subsequent obesity and type 2 dia betes in women and their offspring. Diabetes Care30(Supplement 2), pp.S161-S168.

5. American Diabetes Association, 2020. 14. Management of diabetes in pregnancy: Standards of Medical Care in Diabetes—2020. Diabetes Care43(Supplement 1), pp.S183-S192.

6. Kim, C., Newton, K.M. and Knopp, R.H., 2002. Gestational diabetes and the incidence of type 2 diabetes: a systematic review. Diabetes care25(10), pp.1862-1868.

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