What can help prevent gestational diabetes?

Photo of a pregnant woman with a salad
PantherMedia / Bernd Friedel

Some women can prevent gestational diabetes (diabetes in pregnancy) by getting enough exercise and changing their diet. But it's not clear whether this also prevents complications during pregnancy and childbirth.

Women’s metabolism changes in pregnancy. This can cause their blood sugar levels to increase temporarily. If certain levels are exceeded, the woman is considered to have gestational diabetes. Risk factors include being very overweight, having relatives with diabetes, and having had diabetes in a previous pregnancy.

When can changing your diet prevent gestational diabetes?

Women are generally advised to eat a balanced diet during pregnancy. This means making sure you have a varied diet rather than eating a lot of the same type of food, so the baby gets all the nutrients he or she needs. Most women can simply trust their appetite and don’t need to follow a special diet.

According to the research done so far, the only women who benefit from dietary changes are those who are overweight or obese. They can lower their risk of gestational diabetes by changing their diet with the help of a professional dietitian or nutritionist. The dietary changes can reduce their blood sugar levels and help them put on less weight in pregnancy. In women who have a normal weight, dietary changes don't have a preventive effect.

Research has shown the following for women who are overweight ( > 25) or obese ( > 30):

  • If they didn’t change their diet, 16 out of 100 women were diagnosed with gestational diabetes.
  • If they did change their diet, 6 out of 100 women were diagnosed with gestational diabetes. 

But the studies didn't provide any information about whether the change in diet also influenced the child's birth weight, reduced the risk of complications during the birth, or helped to avoid the need for Cesarean sections.

What type of dietary changes can help prevent gestational diabetes?

Because carbohydrates increase your blood sugar levels, people are usually advised to cut down on carbohydrates (“carbs”) while making sure they still get enough fiber, and generally eat a balanced diet otherwise. Other common advice includes eating three not-too-big main meals and two to three smaller meals per day.

The exact dietary changes to be made will depend on things like how much the woman weighs and how much exercise she gets. Getting special advice from a dietitian or nutritionist can help to avoid adverse effects. It's important to make sure that your body gets enough calories and certain nutrients in pregnancy. So it isn't a good idea to go on a reduced-calorie diet while pregnant.

How much weight gain is okay during pregnancy?

Women who gain a lot of weight in pregnancy have a higher risk of certain health problems and complications during childbirth. Putting on a lot of weight can be a sign of gestational diabetes. There are official recommendations concerning how much weight pregnant women should gain. This depends on how much they weighed beforehand.

  • For women who were underweight before pregnancy ( of less than 18.5): between 12.5 and 18 kilograms of weight gain during pregnancy.
  • For women who had a normal weight before pregnancy ( of between 18.5 and 24.9): between 11.5 and 16 kilograms of weight gain during pregnancy.
  • For women who were overweight before pregnancy ( of between 25 and 29.9): between 7 and 11.5 kilograms of weight gain during pregnancy.
  • For women who were obese before pregnancy ( greater than 30): between 5 and 9 kilograms of weight gain during pregnancy.

Can dietary supplements help?

Research suggests that dietary supplements containing myo-inositol might reduce the risk of gestational diabetes. One possible explanation for this potential effect is that myo-inositol can make insulin work better. But it's not clear whether taking myo-inositol supplements can also reduce the risk of the possible consequences of gestational diabetes, such as complications during the birth. The women in the studies took 2 g of myo-inositol once a day, from the first trimester of pregnancy until the birth of their child. Most of them were overweight.

It is thought that having a vitamin D deficiency can increase the risk of gestational diabetes. But it's not clear whether taking vitamin D supplements has a preventive effect.

Certain dietary supplements, such as omega 3 fatty acids (fish oil), are sometimes claimed to help prevent gestational diabetes. But when omega 3 fatty acids were tested in studies, no preventive effect was found. There is a lack of research on the use of probiotics in this area.

Does getting more exercise help?

A number of studies have looked into whether gestational diabetes is less likely to develop in women who get more exercise from the start of pregnancy than it is in women who don't get much exercise. They found that gestational diabetes was indeed somewhat less common in women who exercised more – regardless of whether they were overweight or had a normal weight.

Studies on women with a normal weight found the following:

  • 5 out of 100 women who didn't get much exercise were diagnosed with gestational diabetes, compared to
  • 3 out of 100 women who exercised more.

Getting more exercise didn't increase the risk of the baby being born too early (preterm birth). It's not clear whether, or how, higher levels of physical activity affect the risk of complications during birth. It's also not clear whether sports and exercise can help to reduce the need for Cesarean sections. There are contradictory research results here.

Some studies have looked into a combination of dietary changes and exercise programs. This approach was also found to help prevent gestational diabetes.

What type of exercise is suitable?

Doing at least 30 minutes of a strenuous activity on about three to four days per week is sometimes enough to lower blood sugar levels. Suitable types of exercise include swimming, cycling and brisk walking. Sports like martial arts, skiing and soccer are too risky during pregnancy. Women who are at greater risk of preterm birth are usually advised to avoid sports altogether. It's best to talk with your doctor or gynecologist about which types of exercise would be suitable for you.

Does medication help?

A number of studies have looked into whether taking metformin has any advantages for very overweight women. Metformin lowers the amount of sugar in your blood. It can be taken in the form of tablets or a solution. But the studies found that metformin didn't prevent gestational diabetes or complications during childbirth. It did cause side effects like diarrhea, though. Because of this, metformin isn't recommended for the prevention of gestational diabetes. It also hasn't been officially approved for the prevention or treatment of gestational diabetes, so it can only be used "off-label" (in a non-approved way).

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IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. informedhealth.org can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

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Updated on October 22, 2020
Next planned update: 2023

Authors/Publishers:

Institute for Quality and Efficiency in Health Care (IQWiG, Germany)

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