Introduction

Most women's blood sugar levels remain normal during pregnancy. But if their blood sugar goes above a certain level, they are considered to have gestational diabetes. This is the medical term for diabetes that occurs during pregnancy (gestation). It affects about 5 out of 100 women.

It is not always clear whether a woman just has slightly higher blood sugar levels or whether she has gestational diabetes. The body’s metabolism changes during pregnancy. It then takes longer for sugar in the bloodstream to be absorbed by the body’s cells after a meal. That's why many pregnant women have higher blood sugar levels than usual. These levels generally return to normal after the baby is born. Having gestational diabetes doesn’t mean that you have developed chronic diabetes.

Gestational diabetes somewhat increases the risk of certain rare birth complications. This risk can usually be lowered by changing your diet, though.

The vast majority of women who develop gestational diabetes experience an otherwise normal pregnancy and go on to give birth to a healthy baby.

At a glance

• About 5 out of 100 pregnant women have more sugar in their blood than usual.
• That can cause the baby to be somewhat bigger and heavier at birth.
• There normally aren't any problems during the birth, though.
• High blood sugar levels can usually be lowered enough by changing your diet and getting more exercise.
• Only a few women need to take insulin, temporarily.

Symptoms

Gestational diabetes usually doesn't cause any noticeable symptoms. If blood sugar levels increase a lot, it may lead to problems such as tiredness, physical weakness or increased thirst, like in other forms of diabetes. These symptoms tend to be mild, and are then often thought to be normal effects of pregnancy.

Causes

The hormones made in the body during pregnancy lead to changes in metabolism (chemical processes in the body). When we digest food and drinks, sugar enters our bloodstream. Due to the changes in pregnant women's metabolism, this sugar is absorbed more slowly by their cells, so their blood sugar levels rise. If their blood sugar regularly goes above a certain level, they are considered to have gestational diabetes.

Risk factors

High blood sugar levels are more common in women who

• are very overweight,
• have had gestational diabetes in the past, or
• have close relatives with diabetes.

Older women are also at greater risk of developing gestational diabetes.

Effects

Gestational diabetes usually doesn’t have any consequences for the mother and child. Babies born to women who have gestational diabetes have a slightly heavier birth weight on average. But this is not a reason for concern.

During the birth of larger babies, the phase after the head has come out often takes longer. If one of the child's shoulders gets stuck in the mother's pelvis (a situation known as “shoulder dystocia”), the child may not get enough oxygen. Midwives and doctors then react quickly, to be on the safe side. This can lead to minor injuries in the child and sometimes in the mother. Although these injuries usually heal well, being in that situation can be distressing for the mother. But emergency situations and more severe injuries are rare.

Higher blood sugar levels also increase the risk of a rare problem during pregnancy known as pre-eclampsia. In pre-eclampsia, more protein than normal is flushed out of your body in urine, your blood pressure increases, and fluid builds up in your body. If left untreated, pre-eclampsia can harm both the mother and the child.

Women who have gestational diabetes are more likely to develop type 2 diabetes later in life.

Diagnosis

The best way to diagnose gestational diabetes is by doing a glucose tolerance test. This test measures how the body reacts to a large amount of glucose (sugar). It is offered in pregnancy between the start of week 24 and the end of week 27.

To find out whether it makes sense to do a glucose tolerance test, you will do what is known as a glucose challenge test first. This involves drinking a glass of water with sugar dissolved in it. One hour later, a sample of blood is taken from a vein in your arm to determine your blood sugar level. If the blood sugar level is found to be high, you will be asked to return to do a glucose tolerance test. This test is similar to the challenge test, but it involves more preparation and takes longer. For instance, it has to be done on an empty stomach.

The test results are documented in your maternity records. In Germany, the costs of glucose tolerance tests are covered by statutory health insurers.

Prevention

Pregnant women who get enough exercise and eat a balanced diet are less likely to develop gestational diabetes than those who are overweight or eat a lot of carbohydrates. But it’s not unusual for pregnant women to have higher blood sugar levels than normal – simply because their metabolism is different.

Treatment

A change in diet is usually enough to make the blood sugar levels return to normal. Women who have gestational diabetes can also seek advice from their doctor or a dietitian. Getting more exercise can help, too.

But some pregnant women have such high blood sugar levels for so long that they have to inject insulin or, in rare cases, take medicine for diabetes.

The doctor will offer to measure the woman’s blood sugar levels again after the baby is born. If her blood sugar levels have returned to normal, no more treatment is needed. All women who develop gestational diabetes are advised to talk with their doctor after the birth to decide whether more tests or lifestyle changes would be a good idea.

Everyday life

Because gestational diabetes usually doesn’t cause any noticeable symptoms, women are often surprised to find out that they have it. Many then start to worry about whether their baby is okay or whether the diabetes will cause problems during birth. Some may be afraid that they’ll still have diabetes after their baby is born. These kinds of concerns can be distressing during pregnancy. So it's important to know that most women with gestational diabetes give birth to healthy children.

The necessary changes in diet and physical activity may take some getting used to at first. But they can soon become a normal part of your daily life and help you keep fit after pregnancy too.

Further information

You will find more information on the management of gestational diabetes in this summary of the German "S3 Guideline."

Sources

• Bennett CJ, Walker RE, Blumfield ML et al. Interventions designed to reduce excessive gestational weight gain can reduce the incidence of gestational diabetes mellitus: A systematic review and meta-analysis of randomised controlled trials. Diabetes Res Clin Pract 2018; 141: 69-79. [PubMed: 29698713]
• Craig L, Sims R, Glasziou P, Thomas R. Women's experiences of a diagnosis of gestational diabetes mellitus: a systematic review. BMC Pregnancy Childbirth 2020; 20(1): 76. [PMC free article: PMC7006162] [PubMed: 32028931]
• Deutsche Diabetes Gesellschaft (DDG), Deutsche Gesellschaft für Gynäkologie und Geburtshilfe (DGGG). Gestationsdiabetes mellitus (GDM): Diagnostik, Therapie und Nachsorge (S3-Leitlinie, in Überarbeitung). AWMF-Registernr.: 057-008. 2018.
• Farrar D, Simmonds M, Bryant M et al. Treatments for gestational diabetes: a systematic review and meta-analysis. BMJ Open 2017; 7(6): e015557. [PMC free article: PMC5734427] [PubMed: 28647726]
• Gemeinsamer Bundesausschuss (G-BA). Richtlinien über die ärztliche Betreuung während der Schwangerschaft und nach der Entbindung ("Mutterschafts-Richtlinien"). 2023.
• Guo XY, Shu J, Fu XH et al. Improving the effectiveness of lifestyle interventions for gestational diabetes prevention: a meta-analysis and meta-regression. BJOG 2019; 126(3): 311-320. [PubMed: 30216635]
• Institute for Quality and Efficiency in Health Care (IQWiG, Germany). Screening for gestational diabetes: Final report; commission S07-01. 2009. [PubMed: 23101079]
• Rayanagoudar G, Hashi AA, Zamora J et al. Quantification of the type 2 diabetes risk in women with gestational diabetes: a systematic review and meta-analysis of 95,750 women. Diabetologia 2016; 59(7): 1403-1411. [PMC free article: PMC4901120] [PubMed: 27073002]

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