Resistance to insulin develops in all mothers during pregnancy. In about 2 to 4 per cent of women this results in temporary diabetes. It happens because pregnant women have less ability to produce extra insulin to overcome this insulin resistance.
Pregnancy diabetes is also called gestational diabetes.
Pregnancy diabetes is more likely:
- if you’re older (over 25)
- if you’re overweight
- if you smoke
- if there is a family history of diabetes
- if you’re from a minority ethnic group
- if there is a previous history of unexplained stillbirth.
- if there is a previous history of a large baby (more than 10lbs, or 4.5kg).
What are the symptoms?
In most cases, pregnancy diabetes has no external symptoms and is detected through screening. Only rarely do the classic symptoms of diabetes appear, eg excessive thirst, frequent urination and tiredness.
How is it diagnosed?
Checking urine for glucose is a routine antenatal test, but is unreliable for diagnosing diabetes.
All mums-to-be should have their blood sugar level checked between 26 and 30 weeks of pregnancy.This is done by testing glucose levels in a sample of blood on two occasions. One of two tests will be used to do this: the random glucose test or the fasting glucose test.
If these tests show you have raised glucose levels, you will need a more detailed test to diagnose diabetes. This is called a glucose tolerance test.
You should also be offered a glucose tolerance test if you are at increased risk of diabetes because of family history, obesity or having had it in a previous pregnancy.
How does it affect the baby?
The importance of pregnancy diabetes is still the subject of some debate, but mothers with it tend to have bigger babies and perhaps more chance of birth defects.
How is it treated?
Pregnancy diabetes is usually treated through diet and exercise. This means:
- increasing the amount you exercise – low-impact activities are safest such as swimming, walking or yoga
- eating regular meals
- keeping an eye on the amount of fat you eat – but remember, a low-fat diet isn’t advised in pregnancy
- reducing salt intake
- eating five portions of fruit and vegetables a day.
- The dietician on your diabetes team will help you draw up a plan.
Regular blood sugar checks are also needed to make sure levels aren’t creeping too high, particularly after meals.
If blood sugar levels remain high, you may need to take insulin through an injection. Quick-acting insulin is used at mealtimes and slow-acting insulin at bedtime.
Until 2008 it was recommended that oral diabetes tablets should not be used in pregnancy and it was advised that women with Type 2 diabetes should convert to insulin treatment before becoming pregnant.
However, the 2008 NICE guidelines for the management of diabetes from preconception to the postnatal period, state that metformin may be used for women with pre-existing type 2 diabetes or gestational diabetes, either in combination with or as an alternative to insulin in the preconception period and during pregnancy.
A large trial from Australian and New Zealand in 2008 showed that metformin when compared with insulin was not associated with increased perinatal complications, either to the mother or baby. Additionally, women preferred metformin to insulin.
How does diabetes affect delivery?
A full-term pregnancy is 40 weeks, but with diabetes labour is often induced (started early) at 38-39 weeks to reduce the risk of stillbirth. As a result, Caesarean section deliveries are more common.
Most babies born to mothers with diabetes don’t require special care, although special attention is given to ensure the baby is not hypoglycaemic (deficient in blood sugar) at birth.
After the birth
Insulin treatment or metformin is usually stopped after the birth, because insulin resistance ends.
Another glucose tolerance test can be done at the six-week postnatal check, to see if treatment needs to continue.
In the long term
Half of women who have pregnancy diabetes go on to develop type 2 diabetes within 10 to 15 years of giving birth. Metformin therapy may prevent this or reduce the number of women affected.