Gestational diabetes develops during pregnancy when your body cannot produce enough insulin to meet increased demands. It affects around 5% of pregnancies in the UK and is diagnosed through a glucose tolerance test (GTT), usually between 24 and 28 weeks. Management involves blood sugar monitoring, dietary changes, and sometimes metformin or insulin. Most gestational diabetes resolves after birth, but it increases your risk of type 2 diabetes later in life.
Gestational diabetes mellitus (GDM) is a type of diabetes that develops during pregnancy in people who did not have diabetes before conceiving. It occurs when your body cannot produce enough insulin to meet the increased demands of pregnancy, leading to higher than normal blood glucose levels.
According to NICE, gestational diabetes affects approximately 5% of pregnancies in the UK, though rates vary by population. It is one of the most common complications of pregnancy and is associated with some increased risks for both parent and baby if not well managed.
The NHS offers a glucose tolerance test to anyone with one or more risk factors. These include a BMI above 30, a previous baby weighing 4.5kg (10lb) or more, gestational diabetes in a previous pregnancy, a parent or sibling with diabetes, South Asian, Black, African-Caribbean, or Middle Eastern heritage.
If you have risk factors, the GTT is usually offered between 24 and 28 weeks of pregnancy. If you had gestational diabetes in a previous pregnancy, you may be offered earlier testing and self-monitoring from the first trimester.
The standard diagnostic test in the UK is the oral glucose tolerance test (OGTT or GTT). You fast overnight, have a fasting blood sugar taken, drink a glucose solution (75g glucose), then have another blood sugar taken 2 hours later.
NICE diagnostic thresholds are: fasting glucose of 5.6 mmol/L or above, or 2-hour glucose of 7.8 mmol/L or above. If either value is met or exceeded, gestational diabetes is diagnosed.
Blood sugar monitoring. You will be given a blood glucose monitor and shown how to test your levels. Typically, you test fasting (first thing in the morning) and 1 hour after each main meal. Target levels are: fasting below 5.3 mmol/L, and 1 hour after meals below 7.8 mmol/L.
Diet. Dietary changes are the first-line treatment. Key principles include choosing low-glycaemic index (GI) carbohydrates such as wholegrain bread, basmati rice, sweet potatoes, and oats. Eating regular meals with protein at each meal. Avoiding sugary drinks, sweets, and refined carbohydrates. Controlling portion sizes of carbohydrates. You will be referred to a specialist diabetes dietitian through the NHS.
Exercise. Regular gentle exercise such as walking for 30 minutes after meals helps lower blood sugar. NICE recommends at least 150 minutes of moderate activity per week during pregnancy where possible.
Medication. If diet and exercise alone do not control blood sugar within 1 to 2 weeks, medication is offered. Metformin is usually the first choice. If metformin is insufficient or not tolerated, insulin injections may be needed. Both are considered safe in pregnancy.
When well managed, most people with gestational diabetes have healthy pregnancies and babies. However, poorly controlled blood sugar can increase the risk of a larger than average baby (macrosomia, over 4kg), which can make delivery more difficult. Premature birth. Pre-eclampsia. Jaundice and low blood sugar in the baby after birth. The baby developing type 2 diabetes later in life.
Good blood sugar control significantly reduces all of these risks, which is why monitoring and management are so important.
Your care will be managed by a specialist team including a diabetic midwife, obstetrician, and diabetologist. If your blood sugar is well controlled and there are no other complications, you may be able to wait for spontaneous labour. However, NICE recommends offering induction or caesarean between 37 and 38+6 weeks if you are on insulin or medication, or from 39 to 40+6 weeks if diet-controlled, to reduce the risks associated with a larger baby.
During labour, your blood sugar will be monitored regularly. If you are on insulin, you may need a glucose and insulin drip (sliding scale) during labour to keep levels stable.
Gestational diabetes usually resolves within hours of delivery. You can stop blood sugar testing and any diabetes medication immediately after birth (your team will confirm this). Your baby''s blood sugar will be checked within the first few hours and they will be encouraged to feed early and frequently.
However, having gestational diabetes means you have a significantly higher risk of developing type 2 diabetes later in life. The NHS recommends a fasting blood sugar test at your 6-week postnatal check and annually thereafter. Maintaining a healthy weight, staying active, and eating a balanced diet after pregnancy can reduce your risk.
NICE targets for gestational diabetes are fasting below 5.3 mmol/L and 1 hour after meals below 7.8 mmol/L. Your diabetes team will confirm your individual targets.
Yes, many people manage gestational diabetes through diet and exercise alone. However, some need metformin or insulin if blood sugar remains above target after 1 to 2 weeks of dietary changes.
Gestational diabetes does not mean your baby will have diabetes at birth. However, both you and your child have an increased risk of developing type 2 diabetes later in life. Healthy lifestyle choices can reduce this risk.
Yes, gestational diabetes usually resolves within hours of delivery. However, you should have annual blood sugar checks because your risk of developing type 2 diabetes is increased.
Yes, breastfeeding is safe and encouraged. It may help your blood sugar return to normal more quickly and can reduce the baby's future diabetes risk.
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