Gestational diabetes

Gestational diabetes is a type of diabetes that affects women during pregnancy. Diabetes is a condition where there is too much glucose (sugar) in the blood.

Normally, the amount of glucose in the blood is controlled by a hormone called insulin. However, during pregnancy, some women have higher than normal levels of glucose in their blood and their body cannot produce enough insulin to transport it all into the cells. This means that the level of glucose in the blood rises.

Two to five in every 100 women giving birth in England and Wales has diabetes. Most of these women have gestational diabetes, and some have type 1 or type 2 diabetes.

Gestational diabetes can be controlled with diet and exercise However, some women with gestational diabetes will need medication to control blood glucose levels.

If gestational diabetes is not detected and controlled, it can increase the risk of birth complications, such as babies being large for their gestational age (Macrosomia).

In most cases, gestational diabetes develops in the third trimester (after 28 weeks) and usually disappears after the baby is born. However, women who develop gestational diabetes are more likely to develop type 2 diabetes later in life.

Gestational diabetes will often not cause any symptoms at all. 

However, high blood glucose (hyperglycaemia) can cause some symptoms, including:

• being thirsty
• having a dry mouth
• needing to urinate frequently
• tiredness
• recurrent infections, such as thrush (a yeast infection)
• blurred vision

During pregnancy, your body produces a number of hormones (chemicals), such as oestrogen, progesterone, and human placental lactogen (HPL). These hormones make your body insulin-resistant, which means your cells respond less well to insulin and the level of glucose in your blood remains high.

The purpose of this hormonal effect is to allow the extra glucose and nutrients in your blood to pass to the foetus (unborn baby) so it can grow.

In order to cope with the increased amount of glucose in your blood, your body should produce more insulin. However, some women cannot produce enough insulin in pregnancy to transport the glucose into the cells, or their body cells are more resistant to insulin. This is known as gestational diabetes.

You may be at increased risk of gestational diabetes if:

• your body mass index (BMI) is 30 or more – you can use the healthy weight calculator to work out your BMI
• you have previously had a baby who weighed 4.5kg (10lbs) or more at birth – the medical term for a birth weight of more than 4kg (8.8lbs) is macrosomic
• you had gestational diabetes in a previous pregnancy
• you have a family history of diabetes – one of your parents or siblings has diabetes
• your family origins are South Asian (specifically India, Pakistan or Bangladesh), black Caribbean or Middle Eastern (specifically Saudi Arabia, United Arab Emirates, Iraq, Jordan, Syria, Oman, Qatar, Kuwait, Lebanon or Egypt)

If you have gestational diabetes, you will be advised about monitoring and controlling your blood glucose (sugar) levels.

For many women, changing diet and more exercise will be enough to control your gestational diabetes. Some women will need medication.

In addition, you will be taught how to monitor your blood glucose, and your unborn baby will be closely monitored.

Don't skip meals. By eating regular, balanced meals which include a starchy carbohydrate with a low Glycaemic Index (GI) you can absorb carbohydrate more slowly helping keep your blood glucose levels stable between meals.

Choose from pasta, basmati or easy cook rice, grainy breads such as granary, pumpernickel and rye, new potatoes, sweet potato and yam, porridge oats, All-Bran and natural muesli. High fibre varieties of starchy foods will also help your digestive system and prevent constipation

If you have gestational diabetes, your unborn baby may be at risk of complications, such as being large for the state of pregnancy. Because of this, you may be offered extra antenatal appointments so your baby can be closely monitored during your pregnancy.

Appointments you may be offered include:

• an ultrasound scan around weeks 18-20 of your pregnancy to check your unborn baby’s heart for any signs of abnormalities (if your gestational diabetes is diagnosed late into your pregnancy you may not be offered this scan) 
• an ultrasound scan at weeks 28, 32, 36 and regular checks from week 38 of the pregnancy to monitor your baby’s growth and the amount of amniotic fluid (the fluid that surrounds them in the womb)

You can wait for labour to start naturally as long as your blood sugars are within normal levels, the ultrasound scans of the baby are normal, and there is no other problem in pregnancy.

If your baby is large for its gestational age (macrosomic), then your doctor or midwife should discuss the birth options with you.

Normal delivery is usually still possible but will depend on the size of the baby.

You should give birth at a hospital where healthcare professionals trained in resuscitating newborn babies are available 24 hours a day.

During labour and the birth, your blood glucose will be measured every hour and kept between 4 to 7 mmol/l. If you have been on insulin during pregnancy, you will be recommended to have an intravenous drip of insulin as well as glucose during labour, to allow careful control of your blood sugar levels.

Around two to four hours after the birth, your newborn baby’s blood glucose will also be measured, this will usually be before the baby’s second feed.

If gestational diabetes goes undetected, or is not managed effectively, it can cause complications for both you and your baby. Controlling your blood glucose (sugar) levels throughout your pregnancy reduces the risk of complications.

Gestational diabetes may increase the risk of:

• placental abruption – the placenta (the organ that links the pregnant woman’s blood supply to her unborn baby’s) starts to come away from the wall of the womb (uterus). This may cause vaginal bleeding and/or constant abdominal pain
• needing to induce labour – when medication is used to start labour artificially (see The pregnancy care planner - inducing labour for more information)
• premature birth (see below)
• macrosomia (see below)
• trauma during the birth – to yourself and your baby
• neonatal hypoglycaemia – your newborn baby has low blood glucose, which can cause poor feeding, blue-tinged skin and irritability 
• perinatal death – the death of your baby around the time of the birth
• development of obesity and /or diabetes later in the baby's life

Premature birth

Gestational diabetes can cause premature birth (your baby being born before week 37 of the pregnancy). This can lead to further complications for your baby, such as:

• respiratory distress syndrome – your baby’s lungs are not fully developed and cannot provide enough oxygen to the rest of their body
• jaundice – your baby’s skin turns yellow when a waste product called bilirubin builds up in the blood

Macrosomia

Gestational diabetes increases the risk of your baby being large for its gestational age, i.e. weighing more than 4kg (8.8lbs). This is known as macrosomia.

Macrosomia occurs during the pregnancy because the excess glucose in the mother’s blood is passed to the foetus (unborn baby). This causes the foetus to produce insulin (a hormone) that allows glucose to enter the cells, which results in growth.

Shoulder dystocia

Macrosomia can lead to a condition called shoulder dystocia. This is when your baby’s head passes through your vagina, but your baby’s shoulder gets stuck behind your pelvic bone (the ring of bone that supports your upper body, also called the hip bones).

Shoulder dystocia can be dangerous as your baby may not be able to breathe while they are stuck. It is estimated to affect 1 in 200 births. For more information, see the Royal College of Obstetricians and Gynaecologists: shoulder dystocia. 

Future conditions

Mother

After having gestational diabetes, you are around seven times more likely to develop type 2 diabetes than women who have had a normal pregnancy.

Type 2 diabetes is when your body does not produce enough insulin, or the body’s cells do not react to the insulin (insulin resistance). See the topic Type 2 diabetes for more information about this condition.

Therefore, it is important your blood glucose is monitored after the birth to check whether or not it returns to normal.

Baby

Your baby may also be at greater risk of developing these conditions in later life:

• diabetes
• obesity (having a body mass index of more than 30)

Future pregnancies

After having gestational diabetes, you are at increased risk of having gestational diabetes in any future pregnancies.

It is very important to speak to your GP if you are planning another pregnancy. They may arrange for you to monitor your own blood glucose from the early stage of your pregnancy. For more information on diagnosing and monitoring high blood glucose, see Gestational diabetes - diagnosis.