What you need to know about gestational diabetes: from risks to treatment

Gestational diabetes refers to the presence of diabetes — high blood sugar levels due to insulin problems — during pregnancy. In the UK, around one in 20 pregnant women will develop gestational diabetes. You do not need to have a history of diabetes before pregnancy to develop gestational diabetes. 

If you’re diagnosed with diabetes early in your pregnancy (in the first trimester), it is more likely that your care team has detected previously undiagnosed diabetes. Gestational diabetes, in which it's the influence of the pregnancy on your body that is causing your body’s cells to not respond effectively to the hormone insulin, usually develops after the first trimester, from around 24 weeks onwards. 

Your risk of gestational diabetes

You’re more at risk of developing gestational diabetes if you’re obese (have a body mass index of 30 or higher) or have a family history of the condition. Genetics play a role in your risk and women of African and Asian descent are more likely to develop gestational diabetes than women of European descent. 

If you developed gestational diabetes in a previous pregnancy, which can be indicated by a large baby size, it’s more likely that you will develop it again. 

Gestational diabetes symptoms

It can be difficult to realise you’re presenting with symptoms of gestational diabetes as symptoms often overlap with common pregnancy symptoms, such as tiredness, gaining weight and urinating more often. 

Consequently, in the UK, gestational diabetes is screened for at 24–28 weeks of pregnancy in women with no history of the condition, and earlier in those with a history of gestational diabetes or other risk factors. 

This involves an oral glucose tolerance test where a blood sample is collected in the morning after not eating or drinking for eight to 10 hours. After this, you will be given a sugary beverage to drink containing 75g of the sugar glucose. After two hours, another blood sample will be collected.

If your fasting blood sugar levels are higher than 5.6 mmol/L or your blood sugar levels two hours after having the sugary drink are 7.8 mmol/L or higher, then you have gestational diabetes. 

The effects of gestational diabetes

Gestational diabetes can have a profound impact on the health of the mother and baby. During pregnancy, it can cause the baby to grow more than usual as the extra sugar (glucose) is passed to the baby through the placenta, which triggers the production of insulin and growth factors. 

Delivering a larger baby increases the chances of complications such as shoulder dystocia where the baby’s head comes out but a shoulder becomes trapped behind the mother’s pubic bone. In more severe cases, gestational diabetes can lead to stillbirth. 

After delivery, the baby is at risk of hypoglycaemia, that is, abnormally low blood sugar levels. This is because the high blood sugar levels in the mother trigger the baby’s pancreas to produce insulin. Insulin causes sugar in the blood to be removed. However, after birth, the baby is no longer receiving high levels of sugar from the mother, leading to low blood sugar levels. 

In the long term, babies born to mothers with gestational diabetes are at higher risk of developing diabetes themselves. This is due to the baby’s genes being affected in the womb by the mother’s high blood sugar levels. 

Gestational diabetes also increases the risk of premature delivery and preeclampsia in the mother, that is high blood pressure during pregnancy and after labour. 

Treating gestational diabetes

If you’re diagnosed with gestational diabetes, you will need to make immediate changes to your diet to reduce the amount of sugar and carbohydrates you consume, as well as to increase your physical activity.

If these changes don’t reduce your blood sugar levels in a week, you will be prescribed the drug metformin or the hormone insulin. If you’re prescribed insulin, you will usually be given short-acting insulin to take with every meal. It is important to note that if your insulin requirements start to reduce in the latter half of your pregnancy, it is a sign that your placenta isn’t working properly and you may need an early delivery. 

Your blood glucose levels and baby’s growth will be closely monitored to ensure your treatment is working. 

What happens after birth?

As soon as you deliver your baby, your pregnancy-related hormones will return to normal, which will cause your gestational diabetes to resolve. If you were taking medication to treat your gestational diabetes, you can then stop taking it. Gestational diabetes can resolve as quickly as the same day of the delivery of your baby. 

However, despite your gestational diabetes resolving, your risk of developing type 2 diabetes in the next five years is raised. It is, therefore, important to continue to look out for signs of diabetes and maintain a healthy lifestyle and dietary habits. 

Preventing gestational diabetes

If you’re at risk of developing gestational diabetes, it is important to take steps to lead a healthier lifestyle before you become pregnant. This means following a healthy, balanced diet, low in sugar and carbohydrates, and regularly exercising. You can speak to a dietitian for advice. 

Once you’re pregnant, you can also seek advice from your midwife. Your midwife will also monitor your weight to check whether you’re at risk — it is normal to put on 11–13.5 kg during pregnancy. Putting on more weight than this by week 20 of your pregnancy is a sign that you may be at high risk of gestational diabetes and need to make further lifestyle changes.