Gestational diabetes

Gestational diabetes is development of high blood sugar (glucose) levels during pregnancy. Strict blood glucose control in pregnant women improves outcomes for both the mother and child.

Alternative names for gestational diabetes

Diabetes in pregnancy

What is gestational diabetes?

Glucose test during pregnancy: Pregnant woman checking the colour of a reagent strip used in a Clinistix urine test. The test detects glucose sugar levels in urine. The brown colouration on the reagent strip indicates a positive (abnormal) result.

Glucose test during pregnancy: Pregnant woman checking the colour of a reagent strip used in a Clinistix urine test. The test detects glucose sugar levels in urine. The brown colouration on the reagent strip indicates a positive (abnormal) result.

Gestational diabetes is any level of sugar in the bloodstream above the normal range, which is first diagnosed during pregnancy. Blood glucose levels usually return to normal after the birth. However, some women who are diagnosed with diabetes during pregnancy may have had diabetes before becoming pregnant, but had not been tested before the pregnancy. In addition, other types of diabetes other than gestational diabetes can appear during pregnancy. In these cases, the diabetes is unlikely to disappear after the baby is born.

What causes gestational diabetes?

The hormones that are secreted by the placenta make the mother’s body cells less responsive to insulin. This is known as insulin resistance. Insulin is the hormone that is secreted by the pancreas and results in the lowering of sugar levels in the bloodstream. It should be noted that all pregnancies have a degree of insulin resistance in order to make maternal nutrients available for the growing foetus. In pregnancy, the pancreas secretes increasing amounts of insulin to overcome the body’s increasing insulin resistance. If a woman does not secrete enough insulin during pregnancy, she is likely to develop gestational diabetes.

What are the signs and symptoms of gestational diabetes?

Gestational diabetes may not cause any symptoms but even so, if not diagnosed, may still cause problems for both mother and baby. Gestational diabetes can result in bigger babies, so women whose babies seem to be big may be offered a test for gestational diabetes.

How common is gestational diabetes? 

In general, gestational diabetes affects 2–9% of pregnancies worldwide. However, these figures vary widely depending on the woman’s ethnicity and obesity. For example, it is more common in women of South Asian origin and women who are overweight before becoming pregnant. It also depends on the methods and levels used to diagnose gestational diabetes.

Is gestational diabetes inherited?

Women from certain ethnic groups or who have a family history are more at risk of having gestational diabetes, but a definite genetic link has not been identified.

How is gestational diabetes diagnosed? 

All pregnant women in the UK should be offered a test to screen for gestational diabetes. Gestational diabetes is usually diagnosed following a glucose tolerance test. For this, blood is taken to measure the glucose level before and two hours after a sugary drink. 

How is gestational diabetes treated?

Treatment begins with lifestyle changes, particularly a change of diet and exercise. If this fails, patients are treated medically with metformin, insulin or both. Metformin is given in the form of tablets. Insulin is given as injections under the skin. Women with gestational diabetes will also need to check their blood glucose levels regularly.

Are there any side-effects to the treatment?

Patients need to ensure that their blood glucose levels are closely monitored and remain within the normal range to avoid any ill-effects. Metformin can cause nausea, vomiting or diarrhoea. Insulin can cause extra weight gain or low blood glucose. In addition, if insulin is given as injections, patients may experience some discomfort around the injection site.

What are the risks to the newborn baby?

If gestational diabetes is diagnosed early and blood glucose levels are closely controlled throughout the pregnancy, this will reduce the risk of complications for the baby.

The baby may put on too much fat, particularly around its abdomen (macrosomia). This can cause problems during the delivery with a greater risk of the shoulder getting stuck (dystocia). In a newborn baby there is a greater risk of the blood glucose level dropping too low and this requires careful monitoring. If the baby develops low blood glucose levels, extra sugar may need to be given to correct this.

What are the longer-term implications of gestational diabetes? 

There is a significantly increased risk of the mother developing type 2 diabetes in the future. She is also more likely to develop gestational diabetes in future pregnancies. Both these risks can be reduced, but not completely prevented, by weight loss and exercise.

The child may be at increased risk of developing weight problems and type 2 diabetes when he or she becomes an adult. Females are also at increased risk of gestational diabetes.

Last reviewed: Mar 2015