It happens because your body cannot produce enough insulin (a hormone important in controlling blood glucose) to meet its extra needs in pregnancy and/or because your body is more resistant than usual to insulin. The result is that blood sugar levels go up. It usually occurs in the second half of pregnancy but can arise earlier.
Any woman can develop gestational diabetes though some women are at more risk than others (see below). Diabetes affects around three to five in every 100 pregnant women (3-5%).
Most women who develop diabetes in pregnancy have healthy pregnancies and healthy babies but occasionally gestational diabetes can cause serious problems, especially if it goes unrecognised. It is associated with stillbirth and premature labour and needs careful monitoring to reduce these risks.
Gestational diabetes starts during pregnancy and stops after the baby is born.
What are the risks of gestational diabetes?
Any form of diabetes - including diabetes that developed before the pregnancy - must be managed carefully because it is associated with complications such as:
- premature birth
- giving birth to a large baby
- having problems during the birth such as shoulder dystocia (where the shoulder gets stuck after delivery of the head)
- developing pre-eclampsia
- developing polyhydramnios – too much fluid around the baby
- the death of the baby around the time of the birth
- your baby developing problems with low blood sugar after birth
- needing an emergency caesarean section or having labour induced
Your baby may also be at risk of becoming obese and/or developing diabetes later in life.
Controlling your levels of blood glucose during pregnancy and labour reduces the risks of all these complications for you and your baby (see below).
Am I at risk of gestational diabetes?
You are at higher risk of developing gestational diabetes if you:
- have a BMI (body mass index) of 30 or higher
- had a previous large baby (weighing 4.5 kg/10lbs or above)
- had gestational diabetes before
- have a parent, brother or sister with diabetes
- your family origin is South Asian, Chinese, African-Caribbean or Middle East.
Treating gestational diabetes
At your first antenatal appointment, your midwife will ask questions to determine whether you have risk factors for gestational diabetes.
If they think you have risk factors, the healthcare team will arrange a simple blood test in early pregnancy and/or a glucose tolerance test (GTT) when you are between 24 and 28 weeks pregnant.
The GTT involves having a blood test first thing in the morning before you’ve had breakfast, the taking a glucose a drink, and then having a second blood test 2 hours later.
This allows the team to work out how your body deals with glucose and whether you have gestational diabetes or not.
If you test positive, you and your baby will be carefully monitored throughout your pregnancy, and you will be shown how to monitor your own glucose levels. If you have had gestational diabetes in a previous pregnancy you will also be offered this test or a testing kit.
Diet and exercise
Changing your diet and exercising regularly are the most important things you can do to improve gestational diabetes. Your healthcare team should give you information on eating healthily and exercising.
Most women who make these changes see an improvement but the small number who don’t are given tablets or insulin injections. If insulin injections are recommended you will be shown how to inject yourself.
Chat to others with gestational diabetes and swap tips and advice in BabyCentre’s gestational diabetes community group.