Causes of gestational diabetes

Gestational diabetes is caused by hormones that you produce during pregnancy. We don’t fully know why some people get it and others don’t. But we do know that some things increase the risk.

What causes gestational diabetes?

Gestational diabetes only develops if you’re pregnant. It tends to be caused by hormones that your body produces. While these hormones are vital for your pregnancy, some of them can lead to changes in your blood sugar (glucose) levels.

Glucose is a type of sugar that comes from foods you eat. It’s your body’s main source of energy and is carried around the body in your blood. Usually, your blood sugar levels are controlled by a hormone called insulin. Insulin lets blood sugar into the body’s cells, so they can use it as energy.

Some pregnancy hormones stop your cells from using insulin as they should. This is called insulin resistance. Less blood sugar gets into your cells, so the amount in your blood rises. 

Your body will usually respond by making more insulin, to try to lower your blood sugar. But if the extra insulin isn’t working right, or your body can’t make enough extra insulin, your blood sugar will stay high. This can lead to gestational diabetes.

Risk factors for gestational diabetes

Anyone can get gestational diabetes during pregnancy. No-one knows quite why some people get it and others don’t. But we do know about some things that increase your risk. These are known as risk factors.

You have an increased risk of gestational diabetes if you:

Your midwife will ask some questions at your first antenatal (‘booking’) appointment, to see if you have any risk factors. If you do, you’ll be offered a test for gestational diabetes

Find out more about tests for gestational diabetes.

"My health was fine until about 26 weeks into my pregnancy. Then at a routine appointment they noticed glucose in my urine, so they said they needed to do a test to rule out gestational diabetes. They told me I had it and asked me to attend the diabetic clinic the following day." 



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NHS website (2022). Gestational diabetes. Available at: (Accessed January 2024) (Page last reviewed 08/12/2022. Next review due 08/12/2025)

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Qiu Y, Zhang X, et al. (2022). 'Association between Polycystic Ovarian Syndrome and Risk of Gestational Diabetes Mellitus: A Meta-Analysis'. Gynecol Obstet Invest. 87(2):150–8.

Review dates
Reviewed: 15 February 2024
Next review: 15 February 2027