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Gestational diabetes

Gestational Diabetes Mellitus (GDM) is a type of diabetes that develops during pregnancy. It usually appears in the second or third trimester and causes higher than normal blood glucose (sugar) levels.

GDM occurs because pregnancy hormones make it harder for your body to use insulin effectively. This process is called insulin resistance. When your body cannot produce enough insulin to keep blood glucose levels within target range, gestational diabetes develops.

For most women, blood glucose levels return to normal after birth. However, having GDM increases the risk of developing type 2 diabetes in the future.

Who is at higher risk?

You are more likely to develop GDM if you:

  • are over 35
  • have a body mass index (BMI) above 30
  • previously had a baby weighing 4.5 kg (10lb) or more
  • had gestational diabetes in a previous pregnancy
  • have a parent or sibling with diabetes
  • are from a South Asian, Black African, Black Caribbean, or Middle Eastern background
  • have polycystic ovary syndrome (PCOS)

Why does gestational diabetes matter?

If blood glucose levels remain above target, there are increased risks for both mother and baby.

Possible risks for baby:

  • Larger than average birth weight (macrosomia)
  • Birth complications
  • Low blood glucose after birth
  • Increased risk of obesity and type 2 diabetes later in life

Possible risks for mother:

  • High blood pressure or pre-eclampsia
  • Higher risk of developing type 2 diabetes in the future

Good blood glucose control significantly reduces these risks.

How is gestational diabetes managed?

The aim of treatment is to keep blood glucose levels within target range to support a healthy pregnancy.

Management may include:

  • Blood glucose monitoring
  • Healthy eating
  • Regular physical activity
  • Medication (metformin or insulin), if needed

Many women are able to manage GDM with diet and lifestyle changes alone.

Healthy eating for gestational diabetes

Healthy eating plays a key role in managing blood glucose levels.

General principles

  • Eat three small-to-moderate meals per day
  • Include 1–3 small snacks if needed
  • Avoid skipping meals
  • Spread carbohydrate intake evenly
  • Choose higher-fibre carbohydrates

Carbohydrates

The goal is not to avoid carbohydrates completely, but to choose the right types and spread them evenly across the day.

Carbohydrates: what to choose and what to limit

  • Wholegrain bread, pitta, or wraps
  • Oats or porridge
  • Brown rice, wholewheat pasta
  • New or sweet potatoes (with skin)
  • Lentils, beans, and chickpeas
  • Sugary drinks and fruit juices
  • Sweets, cakes, pastries
  • Large portions of white bread, white rice, or sugary cereals

Protein at each meal

Including protein helps slow the rise in blood glucose.

Examples:

  • Eggs
  • Greek or natural yoghurt
  • Chicken, turkey
  • Fish
  • Tofu
  • Beans and lentils
  • Nuts and seeds

Fruit and milk

Fruit and milk contain natural sugars. They can still be included but:

  • Stick to one portion of fruit at a time
  • Pair fruit with protein (e.g., yoghurt or nuts)
  • Limit fruit juice and smoothies

Physical activity

Regular physical activity improves insulin sensitivity and helps lower blood glucose levels.

Unless advised otherwise by your maternity team:

  • Aim for 30 minutes of moderate activity most days
  • Brisk walking is often ideal
  • Light activity after meals can help reduce post-meal glucose rises

Always follow advice specific to your pregnancy.

Medication

If blood glucose targets are not met through diet and activity alone, medication may be recommended.

This may include:

  • Metformin tablets
  • Insulin injections

Your healthcare team will discuss what is safest and most appropriate for you and your baby.

Needing medication is not a failure. Gestational diabetes is driven by pregnancy hormones, not just diet.

After your baby is born

After your baby is born, in most cases:

  • blood glucose levels return to normal after delivery
  • you should be offered a blood glucose test 6 to 13 weeks after birth
  • you should have yearly diabetes screening thereafter

To reduce your future risk of type 2 diabetes:

  • Maintain a healthy weight
  • Stay physically active
  • Follow a healthy balanced diet
  • Attend regular health checks

Ongoing support after pregnancy

Having gestational diabetes increases your risk of developing type 2 diabetes in the future. Support is available to help you reduce this risk.

You may be eligible for:

  • The NHS Diabetes Prevention Programme – a free programme that supports people at higher risk of type 2 diabetes to make sustainable lifestyle changes, including healthy eating, physical activity, and weight management.
  • Our local Weight Management Service – providing personalised support with nutrition, physical activity, and behaviour change to help you achieve and maintain a healthy weight after pregnancy.

Speak to your GP, midwife, or practice nurse about referral options.

Frequently asked questions

Did I cause my gestational diabetes?

No. Gestational diabetes is primarily caused by hormonal changes in pregnancy. While weight and lifestyle can influence risk, it is not your fault.

Will my baby have diabetes?

Gestational diabetes does not mean your baby will be born with diabetes. However, maintaining good blood glucose control reduces risks at birth and later in life.

Can I still eat carbohydrates?

Yes. Carbohydrates are important during pregnancy. The key is choosing high-fibre options, managing portion sizes, and spreading them throughout the day.

Will I have diabetes forever?

For most women, blood glucose returns to normal after birth. However, you are at increased risk of developing type 2 diabetes later in life, so ongoing screening is important.