What Causes Gestational Diabetes?

Pregnancy can be a wonderful but often overwhelming time.

Your body goes through many changes, and you work toward a time when your life will likely be very different for the arrival of a new baby.

Perhaps it is your first child, or perhaps you will be welcoming another child to your family. Either way, every pregnancy is different and unique, and sometimes complications can, unfortunately, occur. Gestational diabetes is one of those possible complications.

Usually diagnosed in the second trimester of pregnancy, gestational diabetes is a condition caused by insulin resistance.

It can be challenging for the expectant mother, although with timely identification, effective management, and the right support, it can be treated effectively, and the complications reduced.

Read on to learn more about this type of diabetes-specific to pregnancy, including why some women get gestational diabetes and what you can do if this happens to you. 

How your body uses sugar (glucose)

Glucose is simply a sugar type and can refer to the sugar you eat or your bloodstream’s sugar level.

Glucose is your bodies, and particularly your brain’s preferred energy source. Every cell in your body relies on glucose to function. When you eat carbohydrates, your body breaks them down into glucose units, which are then used by your body for energy. In fact, energy production is one of the primary functions of dietary carbohydrates.

When blood glucose levels rise in the body (which is normal after eating carbohydrates), cells in the pancreas release insulin, signaling cells to take up glucose from the blood. As the cells absorb sugar from the blood, your blood glucose level starts to drop and reach a ‘healthy range.’

The carbohydrate-rich foods you eat are mostly broken down into glucose (except fiber) before entering the bloodstream.

Once in the bloodstream, glucose is taken into the cells in your body.

It is there that it is used to produce something called adenosine triphosphate (ATP). This occurs through a complex process called cellular respiration. The cells in the body can then use ATP for a variety of metabolic jobs (1,2). 

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Pregnancy and high blood sugar

Over time, if blood glucose levels are persistently high, the insulin-producing cells’ demand in the pancreas is high.

This significant demand for these cells can cause them to become overworked, eventually wearing them out and significantly reducing or altogether stopping insulin production. This will lead to type 2 diabetes development, which may need to be treated with insulin injections and preceded by insulin resistance.

While this is an extreme example of the effects of persistently high blood glucose levels, if insulin resistance is identified early, it is easier to manage, diabetes can be prevented or delayed, and generally, the complications that occur are fewer.

For a pregnant woman, there are several other considerations. Physically, your body will go through lots of changes as you progress through your pregnancy.

There are also many hormonal changes happening throughout pregnancy, and some of the hormones you produce can make it more difficult for your body to put insulin to effective use. This, in turn, results in an increased risk of developing insulin resistance. Some women cannot produce enough insulin to overcome this, making it challenging to ensure the sugar (glucose) in your bloodstream is utilized for energy.

If your blood sugar level cannot be managed with effective insulin production, they rise, and gestational diabetes mellitus (herein referred to as gestational diabetes) can occur.

Approximately 16 out of every 100 women in the UK will develop gestational diabetes (3), whereas, in the United States, 2% to 10% of pregnancies yearly are affected by gestational diabetes (4).

Diagnosis of gestational diabetes happens after a blood test, which usually occurs when a woman is between 24 and 28 weeks pregnant (in the second trimester).

Most women don’t have diabetes when they fall pregnant, although some pregnant women will be diagnosed in the first trimester, meaning they probably had diabetes before they fell pregnant (3). 

Why You Get Gestational Diabetes

As previously mentioned, physical and hormonal changes that occur during pregnancy are primarily responsible for gestational diabetes. Among the changes that your body goes through during pregnancy is weight gain.

Weight gain is normal during pregnancy, but it does increase your insulin resistance, which is a risk factor for developing diabetes.

This is no different during pregnancy, and those who are of higher body weight and are clinically identified as overweight or obese are more likely to develop gestational diabetes. 

There are also other risk factors for gestational diabetes to be aware of, including (3,4):

  • Having a first-degree relative who has diabetes (parent or sibling)

  • Being of South Asian, Black or African Caribbean, or Middle Eastern ethnic background 

  • Being of African American, Hispanic/Latino American, Native American, Alaska Native, Native Hawaiian, or Pacific Islander heritage 

  • Having previously had gestational diabetes in an earlier pregnancy

  • Having once had a baby of a higher weight (4.5kg or 10Ib or more)

  • Being aged over 25

  • Having polycystic ovary syndrome (PCOS)

As part of your care during pregnancy, your midwife or consultant should assess your risk for developing gestational diabetes by asking you questions about your history and asking if they can check your weight.

If you feel that the appropriate questions are not being asked, ensure to bring them up yourself. It is vital that you feel empowered throughout your pregnancy and feel armed with as much useful knowledge as possible. Similarly to type 2 diabetes, gestational diabetes carries other risks to health and your babies’ health.

Approximately 50% of women with gestational diabetes will achieve normal blood glucose levels after birth. The other 50% develop type 2 diabetes, which includes the women who were diagnosed during the first trimester and probably had diabetes before they fell pregnant.

Having gestational diabetes can increase your risk of high blood pressure. It can also mean a greater risk of having a large baby that needs to be delivered by cesarean section (C-section birth). 

Unfortunately, there are other potential complications associated with having gestational diabetes.

those who had diabetes before they fell pregnant, some of the long-term problems associated with diabetes can worsen, particularly if the woman has persistent high blood glucose levels (hyperglycemia). These include:

• Eye problems 

Kidney disease 

• High blood pressure 

Preeclampsia is also more common among women with gestational diabetes. Preeclampsia is a serious condition that occurs when you develop high blood pressure and have protein in your urine. It can cause severe complications for you and your baby and can be life-threatening.

When a woman develops preeclampsia, the only cure is to give birth, and then the preeclampsia usually goes away. When a woman with preeclampsia is at full term (37 weeks pregnant or more), a consultant will usually recommend inducing birth to reduce the risks (3,4,5). 

What You Can Do

Coming to terms with a new medical diagnosis at any time is difficult, but particularly so during pregnancy.

As already mentioned, your body will be going through physical and hormonal changes, and the news that you also need to commence treatment can be understandably overwhelming. Thankfully, there are many resources available that can support you to process the news and become empowered to manage your gestational diabetes.  

First and foremost, it is important that you utilize your specialist medical team. This may include a consultant, specialist midwife, dietitian, diabetes educator, and diabetes specialist nurse.

They can support you with decision making, carry out checks on your babies’ health and growth, recommend the best treatment for you, and help you to manage your gestational diabetes. They can also offer you support with your mental health, should you need it. 

Feeling empowered when it comes to managing medical conditions often means taking control of your treatment, which is no different for gestational diabetes. There are things that you can do to help manage your gestational diabetes, in addition to attending appointments. These include (4):

  • Eating a healthy diet. Attempting weight loss throughout pregnancy is not recommended, even if you do have diabetes. Yet, there are still benefits to eating well and getting the right balance of nutrients.

    In general, a healthy gestational diabetes diet consists of plenty of fruit and vegetables, other fiber-rich foods such as wholegrain carbohydrates and legumes, healthy fats including oily fish and nuts and seeds, dairy foods, or calcium-rich alternatives, and low amounts of added sugars. A registered dietitian can support you with your diet if you have gestational diabetes and would like some support.

  • Physical activity. Moderately intense exercise such as brisk walking can lower your blood sugar levels and improve your insulin sensitivity. A brisk 30-minute walk a few times per week can be an incredibly healthy addition to your pregnancy care routine. Be sure to check with your doctor before starting any new forms of exercise when you are pregnant. Exercise can help to maintain healthy blood glucose levels and is important for overall physical and mental health. It can also help you to maintain a healthy weight

  • Monitoring your blood glucose levels to make sure they stay within the healthy range.  

  • Take supplements where necessary. Pregnant women wanting to conceive are recommended to take folic acid to help prevent neural tube defects (NTD’s). The standard dose recommended during pregnancy and up to the beginning of the second trimester is 400 micrograms of folic acid per day.

    For some women, including those with diabetes, a higher dose may be recommended. This higher dose is 5mg of folic acid per day. Always speak with your doctor before you supplement to check it is indicated and that you get the correct dose (6). 

In the even that you cannot effectively manage your gestational diabetes with healthy eating and exercise, medication will be required. This will most commonly be metformin, and many women also need insulin injections (4). Diabetes UK has some fantastic additional resources on gestational diabetes, including more information on treatment and several useful meals and snack ideas. 

As always, it is also important to ensure you utilize the support of your specialist medical team. You may need to adjust your medications (if you are on any), and they can advise on a variety of topics to help you enjoy a healthy pregnancy and have a healthy baby. These may include nutrition, physical and mental wellbeing, and pregnancy and birth preparation. 


Developing gestational diabetes during pregnancy can be extremely worrying. Some complications can occur during and after pregnancy as a result of having gestational diabetes, and there are risk factors associated with the development of the condition.

Yet, if you are at risk, you can take steps to reduce this risk; and if you have already been diagnosed, you must seek support. With early identification and the right support, gestational diabetes can be managed, and the incidence of complications can decrease.

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  1. National Institute of Diabetes and Digestive and Kidney Diseases. (2018). Online. Available at: https://www.niddk.nih.gov/health-information/diabetes/overview/what-is-diabetes/prediabetes-insulin-resistance#causes Accessed on: 31/10/2020
  2. Diabetes UK. Insulin and Diabetes. (2020). Online. Available at: https://www.diabetes.org.uk/guide-to-diabetes/managing-your-diabetes/treating-your-diabetes/insulin Accessed on 1/11/2020
  3. Diabetes UK. What is Gestational Diabetes? (2020). Online. Available: https://www.diabetes.org.uk/diabetes-the-basics/gestational-diabetes Accessed on 1/11/2020
  4. CDC: Centers for Disease Control and Prevention. (2019). Online. Gestational Diabetes. Available at: https://www.cdc.gov/diabetes/basics/gestational.html Accessed on 1/11/2020
  5. National Institute of Diabetes and Digestive and Kidney Diseases. Pregnancy if you have diabetes. (2017). Online. Available at: https://www.niddk.nih.gov/health-information/diabetes/diabetes-pregnancy#baby accessed on: 2/11/2020
  6. NHS. Vitamins, supplements and nutrition in pregnancy. (2020). Online. Available at: https://www.nhs.uk/conditions/pregnancy-and-baby/vitamins-minerals-supplements-pregnant/ accessed 2/11/2020

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