Diabetes in pregnancy
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 giving birth. However, some women who are diagnosed with diabetes during pregnancy may have had underlying diabetes before becoming pregnant, but this had not been tested or diagnosed 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.
Insulin is the hormone that is secreted by the pancreas and results in the lowering of sugar levels in the bloodstream. In pregnancy, the hormones that are secreted by the placenta make the mother’s body less responsive to insulin. This is known as insulin resistance. It should be noted that all pregnancies have a degree of insulin resistance in order to make nutrients in the maternal bloodstream available for the growing foetus. During 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.
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 (macrosomia), so a pregnant woman whose foetus seems to be big may be offered a test for gestational diabetes.
Some pregnant women with more severe gestational diabetes may have significantly higher blood glucose level. They may experience symptoms such as elevated thirst, frequent urination and tiredness.
In general, gestational diabetes affects 2–9% of pregnancies worldwide. However, these figures vary widely depending on the woman’s ethnicity and weight. For example, gestational diabetes is more common in women of South Asian origin and in women who were overweight before becoming pregnant. It also depends on the methods and levels used to diagnose gestational diabetes.
Women from certain ethnic groups (South Asian, Black, African-Caribbean or Middle-Eastern) or who have a family history are more at risk of having gestational diabetes, but a definite genetic link has not been identified.
All pregnant women in the UK should be offered a test to screen for gestational diabetes. Gestational diabetes is usually diagnosed following an oralglucose tolerance test. For this, blood is taken to measure the glucose level before and two hours after a sugary drink; if the blood glucose concentration remains elevated two hours after that drink, this suggests an impaired glucose tolerance test and a problem either making or responding to the hormone insulin.
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 a drug which increases the sensitivity of cells and tissues to insulin, given in the form of tablets. Insulin, which increases glucose breakdown in cells, is given as injections under the skin. Some patients may be prescribed with a tablet called glibenclamide, which stimulates the pancreas to release more insulin.
Women with gestational diabetes will also need to check their blood glucose levels regularly to ensure that they are managing their gestational diabetes.
Patients need to ensure that their blood glucose levels are closely monitored and remain within the normal range to avoid any ill-effects for them or their baby. Metformin can cause nausea, vomiting or diarrhoea. Insulin can cause extra weight gain or symptoms associated with low blood glucose (e.g. dizziness and sweating). In addition, if insulin is given as injections, patients may experience some discomfort around the injection site.
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.
If gestational diabetes is not effectively managed, the excess blood glucose may cause the baby to produce too much insulin. This can cause the baby to put on too much fat, particularly around its abdomen (macrosomia) which, in turn, can cause problems during the delivery with a greater risk of the shoulder getting stuck (dystocia). In a new-born 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 the baby to correct this.
Gestational diabetes may also lead to premature labour or stillbirth, although this is quite rare.
There is a significantly increased risk of the mother going on to develop type 2 diabetes in the future. She is also more likely to develop gestational diabetes in any subsequent pregnancies. Both these risks can be reduced, but not completely prevented, by weight loss and exercise.
A child born to a mother with gestational diabetes may be at increased risk of developing weight problems and type 2 diabetes when he or she becomes an adult. Girls born to a mum with gestational diabetes are also at increased risk of suffering gestational diabetes in their own pregnancies.
Last reviewed: Nov 2021