Introduction

Most women's blood sugar levels remain normal during pregnancy. But if their blood sugar levels go above a certain value, 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's 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 childbirth. 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.

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 understood to be typical signs of gestational diabetes.

Causes

The hormones produced by the body during pregnancy cause changes in the woman's metabolism (chemical processes in her 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 certain levels are regularly exceeded, the woman is 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 the body in the urine, blood pressure increases, and fluid builds up in the 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 of diagnosing 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 between 24 and 28 weeks of pregnancy (during the second trimester).

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

Prevention

Women who get enough exercise and eat a balanced diet are less likely to develop gestational diabetes than women 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. Special dietary counseling can be helpful too. Another way to lower your blood sugar levels is by getting more exercise.

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 the vast majority of 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.

Sources

• Bennett CJ, Walker RE, Blumfield ML, Gwini SM, Ma J, Wang F 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). AWMF-Registernr.: 057-008. February 28, 2018.
• Farrar D, Simmonds M, Bryant M, Sheldon TA, Tuffnell D, Golder S 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 des G-BA über die ärztliche Betreuung während der Schwangerschaft und nach der Entbindung („Mutterschafts-Richtlinien“). February 20, 2020.
• Guo XY, Shu J, Fu XH, Chen XP, Zhang L, Ji MX 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; Version 1.1. August 25, 2009. (IQWiG reports; Volume 58).
• Rayanagoudar G, Hashi AA, Zamora J, Khan KS, Hitman GA, Thangaratinam S. 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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