Whenever you eat, your body produces a hormone called insulin that regulates the sugar in your blood. When you're pregnant, your body needs extra insulin, and if you don't produce enough, your blood-glucose (sugar) levels can become abnormally high – and this is known as gestational diabetes.

Gestational diabetes increases the likelihood of problems, such as high blood pressure or pre-eclampsia, a potentially dangerous pregnancy condition.

How is it detected?
At each antenatal appointment, your urine will be tested for sugar, which can indicate raised levels of blood glucose. Lots of pregnant women have raised glucose levels without having diabetes, so try not to worry if this happens to you – but you'll probably be referred for more tests.

Initially, you'll have a blood test, and if this also shows raised glucose levels, you'll be given a glucose-tolerance test at your local hospital. This involves a fast (generally an hour or two), followed by a blood test. You'll then be given a sugary drink, and be tested again to see how your body metabolises the sugar. If your blood glucose levels are still high after two hours, this indicates that your body is not producing enough insulin.

What's the treatment?
In many cases, adopting a diet that is high in starchy carbohydrates, fruit and vegetables and low in fat, sugar and salt, will be all that is needed to manage pregnancy diabetes. You may also be advised to eat little and often, to encourage your body to produce insulin, and you'll need regular blood glucose checks to monitor your condition.

You may be given a glucose meter so that you can do your own finger-prick tests to keep an eye on your blood-glucose levels, and you'll probably be scheduled for regular scans to check that your baby isn't growing too large.

Between 10 and 30 percent of women with gestational diabetes will need extra insulin; if you do, you can be taught to inject it yourself.

Will it affect my baby?
In most cases, gestational diabetes doesn't develop until the second trimester, by which time your baby's internal organs have formed, so any risks to him are low.

If the condition isn't effectively managed, however, too much glucose can cross the placenta and lead to your baby laying down too much fat. A very large baby can be at risk of premature labour and delivery by caesarean section, and if there are any doubts about your baby's wellbeing, you may be induced at around 38 weeks.

After your baby's born, he may have low blood-glucose levels, or hypoglycaemia, and will need to be checked regularly with a heel-prick test until they return to normal.

Your blood glucose levels should return to normal after the birth, but you'll need a follow-up glucose-tolerance test after six weeks.

Am I at risk?
You're more likely to develop gestational diabetes if you:

  • are over 35
  • are overweight
  • have a family history of diabetes
  • had gestational diabetes in a previous pregnancy
  • have previously had a big baby
  • have had two or more pregnancies already
  • are Asian or Afro-Caribbean