Inability of the tissues to absorb glucose from the bloodstream during pregnancy due to a lack of the hormone insulin
- More common over the age of 30
- A family history of diabetes mellitus is a risk factor
- Being overweight is a risk factor
During the course of pregnancy, up to 1 in 50 women temporarily develops diabetes mellitus. The condition is called gestational diabetes. Normally, the hormone insulin, which is produced by the pancreas, enables body cells to absorb glucose from the bloodstream. During pregnancy, additional hormones, which have an anti-insulin effect, are produced by the placenta. If the body does not produce enough insulin to counter this effect, the result is high levels of glucose in the blood and gestational diabetes.
Diabetes developing in pregnancy is more common in women over the age of 30, women who are overweight, and those who have a family history of diabetes mellitus. Gestational diabetes can usually be controlled by a special diet.
In most cases, gestational diabetes disappears after the birth of the baby, but about 1 in 3 women who has had gestational diabetes develops permanent type 2 diabetes mellitus, often within 5 years of pregnancy.
What are the symptoms?
Many women with gestational diabetes do not develop symptoms. Others may develop symptoms that include:
Increased thirst and appetite.
Passing large amounts of urine.
If gestational diabetes is not controlled, the fetus may gain an excessive amount of weight and have difficulty passing through the mother’s pelvis. Labour may then be particularly difficult (see Problems during delivery). Babies born to mothers with gestational diabetes are also at risk of having low blood sugar levels at birth. Women whose diabetes cannot be controlled have a greater risk of a stillbirth.
How is it diagnosed?
Diabetes mellitus is usually detected when urine and/or blood tests reveal the presence of glucose. Your urine will be tested for glucose at each antenatal visit. If glucose is found in your urine, your doctor may arrange for a glucose tolerance test, in which you are given a sugar solution to drink and a sample of your blood is tested. If your blood shows higher glucose levels than would normally be anticipated, the diagnosis of gestational diabetes is confirmed. Your doctor may also suggest that you have the glucose tolerance test if you have had an unexplained stillbirth in the past or if you have given birth to a larger than average baby. Your doctor may also suggest that you have the test if diabetes mellitus runs in your family because this may increase your risk of developing gestational diabetes.
What is the treatment?
If you have gestational diabetes, your doctor will recommend that you follow a modified diet that contains less sugar than normal and greater amounts of fibre and starchy carbohydrates. Some women also need insulin injections. You may be advised to test your blood sugar levels at home (see Monitoring your blood glucose). More frequent antenatal visits than usual may be necessary, and you may also need to have extra ultrasound scans (see Ultrasound scanning in pregnancy).
For most women with gestational diabetes, pregnancy progresses safely to about 40 weeks, and vaginal delivery is possible. However, if diabetes becomes difficult to control, early induction of labour may be necessary. If the fetus is very large, the doctor may carry out a caesarean section to avoid a difficult vaginal delivery.
After delivery, your blood sugar levels and those of your baby will be monitored. If the baby’s blood sugar level is low, he or she may need to be admitted to a special care baby unit for treatment. Since you may be at risk of developing permanent diabetes mellitus after pregnancy, you will be given a glucose tolerance test at your 6-week postnatal checkup.
What is the prognosis?
Usually, glucose levels return to normal soon after delivery of the baby, and you should be able to resume your normal diet. If you were having insulin injections, they can be stopped. However, you are likely to develop diabetes during future pregnancies and you may be at risk of developing diabetes in later life.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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