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What are the risks of gestational diabetes?

Having gestational diabetes holds risks to the mother and baby, but women tell us they are not always clear exactly what those risks are.

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A risk means there is a chance that something might happen. With every pregnancy there are some risks, but if you have gestational diabetes your risks of some things will be increased. Managing your blood sugar level brings these risks right down again though and most women with gestational diabetes have healthy pregnancies and healthy babies.

These things are very unlikely to happen to you, but understanding the risks may help you see why it is important that you follow your healthcare team’s advice.

The risks linked to gestational diabetes are caused by blood glucose levels being too high. If you can keep your blood glucose as close as possible to the ideal level, your risks will be reduced.

Risk of having a large baby (macrosomia)

If your blood glucose level is high, it can cause high blood glucose levels in your baby. Your baby will produce more insulin in response, just like you do. This can make your baby grow larger than normal. This is called macrosomia. Babies weighing more than 4kg (8lb 8oz) at birth are called macrosomic.

Macrosomia increases the risk of:

Birth trauma - either the mother or baby can be affected when it is difficult for the baby to be born. Trauma may include physical symptoms, such as bone fractures or nerve damage for the baby, or tearing and severe bleeding for the mother as well as psychological distress.
Shoulder dystocia - where the baby’s shoulder is stuck in your pelvis once the head has been born. This can squash the umbilical cord, so the team need to use additional interventions to deliver the baby quickly and safely.

It means you may have labour induced early or to have a caesarean section so that your baby is born safely. Your baby's weight will be monitored carefully in pregnancy to see whether these interventions are needed.

Keeping your glucose levels under control throughout your pregnancy, and during labour reduces these risks.

Risk of premature birth

Gestational diabetes is linked to an increased risk of preterm birth (giving birth before 37 weeks). This may be because induction/caesarean section is recommended for other complications, or it may be spontaneous premature birth in which the reason is not clear.

One cause of preterm birth can be damage to the placenta. During pregnancy the placenta, which connects the baby to your blood supply, produces high levels of hormones that affect the action of insulin in your cells, raising your blood sugar. As your baby grows, the placenta produces more and more insulin-counteracting hormones. In gestational diabetes, the placental hormones can mean a rise in blood sugar to a level that can affect the functioning of the placenta and the growth and development of the baby.

If blood sugar levels are managed this risk is lessened.

Risk of stillbirth at the end of pregnancy

For all women, the risk of stillbirth or the baby dying shortly after the birth increases when the pregnancy goes over 42 weeks, so all women in the UK who go past their due date are offered an induction date set before 42 weeks.

One study, however, has shown that for women with gestational diabetes there is an increased risk of stillbirth after 40 weeks plus 6 days and so, if you live in England or Wales, you will be advised to have your labour induced before you reach this point.

In Scotland, most women with diabetes in pregnancy are induced within 40 weeks. The SIGN guidance says that this decision should be determined on an individual basis.

Please note that even though your risk of stillbirth is increased it is still low.

'You find all these things out, and they are all incredibly rare, but I did really worry. That’s why I was so motivated to manage my glucose levels.' Beth

Risk of low blood sugar in the baby after the birth

Sometimes babies of mothers with gestational diabetes develop low blood sugar shortly after birth because their own insulin production is high. This is called neonatal hypoglycaemia. This can be treated with prompt feeding and sometimes an intravenous glucose solution.

If left untreated, hypoglycaemia can cause damage to the baby’s brain that can lead to developmental delay, but if your team know that you have gestational diabetes then your baby’s glucose levels will be tested to check there are no problems with glucose levels.

Keeping the risks in perspective

It is natural to find these possibilities worrying. The truth is that there are risks associated with gestational diabetes – and although treatment can significantly lessen the risks, it can’t remove them altogether. But it is important to put this into perspective. Every pregnancy has some risks, whether or not the mother has gestational diabetes. Being diagnosed is a good step towards helping you reduce those risks. By getting support from your healthcare team, and following the guidance you can lower the risks as far as possible.

'I suppose everybody who is pregnant has something – there’s always something that doesn’t go right – but I was really worried. You just want it to be perfect, don’t you.' Kate

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Treatment for gestational diabetes
Gestational diabetes is treated by making changes to diet and exercise to manage blood sugar levels, and using medication if necessary.
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Symptoms of gestational diabetes
Women with gestational diabetes often do not have any symptoms at all, and this is why women are all monitored for it by routine checks in pregnancy.
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Testing for gestational diabetes
Gestational diabetes is one of the conditions that midwives will be looking out for during your normal appointment schedule. If you have it, it will be spotted through tests.
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Gestational diabetes and giving birth
The emphasis is on trying to keep the birth as normal as possible unless there is a particular reason to do things differently.
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Longer term implications of gestational diabetes
If you have had gestational diabetes in pregnancy you will be at higher risk of having it again in a next pregnancy and of getting type 2 diabetes in later life.
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Causes of gestational diabetes
Clinicians and researchers do not understand yet exactly why some women get gestational diabetes and others don't, but we know that there are some life and family factors that make it more likely in some women.