Gestational Diabetes Mellitus (GDM) | Hull University Teaching Hospitals NHS Trust

Reference Number: HEY816-2023
Departments: Maternity Services
Last Updated: 3 April 2023

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Introduction

This leaflet has been produced to give you general information about your condition. Most of your questions should have been answered by this leaflet. It is not intended to replace the discussion between you and your doctor but may act as a starting point for discussion. If after reading it you have any concerns or require further explanation, please discuss this with a member of the healthcare team who has been caring for you.

What is Gestational Diabetes Mellitus (GDM)?

Gestational Diabetes Mellitus (GDM) is a condition which develops during pregnancy and leads to high levels of glucose in the blood.

Glucose comes from the digestion of carbohydrate foods such as bread, rice, potatoes, cereals, pasta, fruit and sugar. Your liver also makes glucose. We need glucose to live, as it is our main source of energy.

When glucose enters the blood, the pancreas releases insulin. Insulin is a hormone that acts like a ‘key’ to ‘unlock’ cells allowing glucose to enter cells from the blood. The cells can use the glucose as fuel to release energy. Insulin therefore helps to lower blood glucose levels and to keep them in the normal range.

During pregnancy your body needs more insulin than usual. This is because the placenta releases hormones which make your body more resistant to insulin. In most women the body can produce enough insulin to overcome this resistance. However, in some women they are not able to produce enough insulin and therefore blood glucose levels rise to above normal levels.

What factors increase the risk of GDM?

Gestational diabetes in previous pregnancies.
Previous large baby over 4.5 kilograms (4.5kg).
Body mass index (BMI) over 30 kilograms per square metre squared (30kg/m²).
Family history of diabetes.
Minority ethnic family origin with a high prevalence of diabetes.
Previous stillbirth.

How is GDM diagnosed?

If you have any of the above risk factors, you will be checked for GDM at your booking appointment with the midwife, and again at 28 weeks pregnancy.

GDM is diagnosed by an Oral Glucose Tolerance Test (OGTT) – The results will show as a plasma glucose level being greater than 5.6 millimoles per litre (>5.6mmol/l) before the OGTT or greater than 7.8 millimoles (>7.8mmol/l) per litre 2 hours after the OGTT if you have GDM.

If you have had GDM in a previous pregnancy you may be asked to start self-monitoring early on in this pregnancy rather than have an OGTT.

GDM may also be diagnosed if you have a HbA1c level of 41 millimoles per mole (41mmol/mol) or more at booking or 39 millimoles per mole (39mmol/mol) or more at 28 weeks.

A HbA1c test is a simple blood test that measures your average blood sugar levels over the past 3 months. It is one of the commonly used tests to diagnose pre-diabetes and diabetes, and is also the main test to help you and your health care team manage your diabetes.

What are the risks of GDM?

The most common problem associated with GDM is your baby growing too big in your uterus (womb). This is called macrosomia. This is because the growing baby is receiving too much glucose via your placenta. This may cause problems with delivery as the baby grows too large to deliver safely through the vagina. This will mean that your baby may need to be delivered by caesarean section. You may be offered additional scans during pregnancy to assess the growth of your baby. The Obstetrician will discuss with you the risks and benefits of delivery either normally (vaginally) or by caesarean section so that you have an informed choice about the safest way to deliver your baby.

GDM also increases the risk of:

stillbirth
raised blood pressure during the pregnancy (pre-eclampsia)
preterm (early) labour

These risks can be significantly reduced with the support of your health care team.

What steps can I take to reduce the risks?

There are simple steps that you can take:

monitor blood glucose regularly
lifestyle changes – diet and exercise
medications.

Blood glucose (BG) monitoring

Regular blood glucose (BG) monitoring can help you keep track of your progress, and your healthcare team to identify any treatment needs at an early stage. You will be given a diary to record your values. These will be reviewed by your healthcare team weekly.

Test before breakfast – your BG reading should be less than 5.3 millimoles per litre (5.3 mmol/l)
Test one hour after meals – your BG reading should be less than 7.8 millimoles per litre (7.8 mmol/l)

Note – if you are on insulin to help with blood glucose control, you will be asked to test your blood glucose levels more often.

Lifestyle changes – diet and activity

It is carbohydrate foods that increase blood glucose levels. The more carbohydrate that you eat at a meal or snack, the higher your blood glucose can rise.

To help keep blood glucose in target, you can:

Reduce the carbohydrate portion at meals and spread carbohydrate foods throughout the day.
Choose different types of carbohydrates.

Ensure that you stay active.

Which are the carbohydrate foods?

Food	Examples
Bread	All types including white, wholemeal, wraps, bagels, tortillas, naans
Rice and grains	All types including white, brown, basmati, pilau rice, bulgar wheat, quinoa
Pasta, couscous and noodles	All types, fresh, dried or tinned
Potato	All types including sweet potato, chips, mashed, boiled, fresh, frozen or tinned
Breakfast cereals	All including porridge, muesli and granolas
Batters, coated foods	Yorkshire pudding, pancakes and batter mixes
Coated foods	Includes eg. Fish Fingers, battered cod and breaded chicken
Fruits	All types – dried, fresh, frozen and canned including smoothies and fruit snack bars
Dairy	Milk and milk products including yogurt, ice cream and custard

Sugars	Including syrup, honey, treacle, jam and marmalade and sweets
Products made from flour	Includes pies, sausage rolls, pastries, cakes and biscuits
Processed meats	Includes burgers, sausages with added starch/wheat flour
Potato/maize/corn/rice/snacks and biscuits	Includes crisps, tortillas, popcorn, puffed wheat, rice cakes, crispbreads and crackers

To help keep blood glucose in target, you can reduce carbohydrate portions at meals and spread carbohydrates through the day

Aim for 3 meals a day, with carbohydrates no more than a quarter of your plate at each meal (approximately a fist sized portion), with up to 2 low carbohydrate snacks

You may be given individual advice to limit carbohydrate portions at meals, or a suggested amount of carbohydrate in grams, based on your blood glucose values.

Including protein from meat, fish, eggs, cheese and nuts can help to keep you fuller for longer, so your meals and snacks are more satisfying.

Including vegetables and salad increases fibre in meals and slows digestion. This helps to release glucose into the blood more slowly.

Top tips for snacks

Include protein and fibre with your snacks as you would a meal to prevent high blood glucose levels before your next meal!

Snack swaps!

3 x digestive biscuits (200 kilocalories (200 kcal), (30 grams (30g) carbohydrate) for 1 x digestive biscuit and a small piece of cheese (200 kilocalories (200kcal), 10 grams (10g) carbohydrate)
Large banana (120 kilocalories (120kcal), 30 grams (30g) carbohydrate) for a small pot Greek yoghurt and a portion of blueberries (110 kilocalories (110kcal), 10 grams (10g) carbohydrate)
Jam doughnut (200 kilocalories (200kcal), 30 grams (30g) carbohydrate) for a medium apple with peanut butter (150 kilocalories (150kcal), 15 grams (15g) carbohydrate)
Medium bar milk chocolate (300 kilocalories (300kcal), 35 grams (35g) carbohydrate) for a pot of sugar free jelly and a portion strawberries (50 kilocalories (50kcal), 12 grams (12g) carbohydrate.

Meal ideas

Aim to eat 3 meals and up to 2 snacks per day to keep blood glucose levels stable.

Menu ideas

Breakfast 20 to 30 grams carbohydrate – examples include one of the following:

2 small slices of toast with spread
4 tablespoons cereal such as cornflakes/bran flakes/rice cereal with milk
2 wheat biscuits with milk
2 poached or scrambled eggs on 1 slice of toast
small pot yoghurt with 1 piece of fruit
30 grams (30g) porridge oats made with milk

Lunch 40 to 50 grams carbohydrate – examples include one of the following:

2 medium sliced bread sandwich with protein filling such as meat/cheese/egg/ fish with piece of fruit
small tin of baked beans on 1 slice toast and piece of fruit
small jacket potato (weighing 200 grams (200g) when cooked) with salad and cottage cheese/cheese.

Evening meal 40 to 50 grams carbohydrate – examples include one of the following:

4 tablespoons pasta with meat/fish and salad/vegetables
4 tablespoons basmati rice with meat/fish and salad/vegetables
4 egg size potatoes with meat/fish and salad/vegetable
small jacket potato (weighing 200 grams (200g) when cooked) with meat/fish and salad/vegetables

Follow with a small pot of diet yoghurt or piece of fruit, small scoop ice cream (weighing approximately 40 grams (40g)).

Try and avoid sauces as they can contain carbohydrate eg sweet and sour, béchamel sauces and gravies.

Snack Ideas (10 to 15 grams carbohydrate)

Small piece of fruit eg apple/pear/banana
2 crispbreads and low fat cheese
Small pot diet/light yoghurt
2 x rich tea, malted milk or plain biscuits

Carbohydrate-free snacks can be eaten at any time:

Raw vegetables/salad with humous/salsa dip/cottage cheese
Handful nuts/mixed seeds
Olives/sundried tomatoes
Sugar free jelly
Beef/fish jerky

*For more meal ideas, go to diabetes UK gestational diabetes page – link at the end

Choose different types of carbohydrates

High fibre, starchy carbohydrate foods contain more fibre, vitamins and minerals than processed and refined carbohydrates. The added fibre helps to slow the release of glucose into the blood, keeping levels more stable, and also helps to keep you fuller for longer.

Pasta and noodles

Limit or avoid white and refined pasta and noodles but choose brown if available.

Bread, pitta and chapatti

Limit or avoid white, brown or wholemeal and choose sourdough, wholegrain, granary, seeded, rye or pumpernickel.

Rice, grains and pulses

Limit or avoid white, instant and long grain rice but choose brown rice, pearl barley, quinoa, chickpeas or lentils.

Potatoes

Limit or avoid white, including baked, mashed or boiled but choose sweet or new potatoes.

Cereals

Limit or avoid frosted, chocolate, cornflakes, puffs and fruity muesli but choose oats (porridge) and nutty muesli.

Biscuit, crackers and snacks

Limit or avoid crisps, corn, maize snacks and biscuits with jam, icing and chocolate but choose unsweetened popcorn, oatcakes, plain biscuits and crackers.

Processed foods

Limit or avoid any breaded or battered products but choose boiled or steamed fish and meat.

Other top tips

Fruit and vegetables

Aim for 5 portions per day. A portion is around a handful or 80 grams (80g).

Vegetables and salad will not affect your glucose levels so can be eaten freely. They are also a good source of fibre, vitamins and minerals.

Fruits should be limited as they contain carbohydrate. Only have one portion at a time and up to 2 portions per day. Avoid fruit smoothies and fruit juices as these can be very high in sugar.

Milk and other dairy products

Milk does contain carbohydrate, but relatively small amounts. Milk is also an excellent source of protein and minerals, including calcium, essential for your baby’s development.

Aim for 3 portions of dairy per day, eg 1 small glass milk (200 millilitres (200ml), 1 pot diet yoghurt (150 grams (150g)), 30 grams (30g) of any cheese.

Unsweetened nut and coconut milks are suitable alternatives to dairy products.

Drinks

Fruit juices and smoothies can be very high in sugars, so are best avoided.

Carbonated sugary drinks including Coca-cola, Pepsi, Lucozade, Sports drinks are high in sugar and should be avoided. Sugar-free/diet/zero versions have artificial sweeteners eg. aspartame or saccharin and are safe to take in small amounts.

Diabetic foods

These are not recommended as they are more expensive and can have a laxative effect.

Increase activity levels

Activity increases the amount of glucose used by your muscles for energy, so it helps to lower your blood glucose levels. Also, being active helps the body use insulin more efficiently.

There are lots of other health benefits – being active can help with weight loss, lowering blood pressure and reducing stress and helping sleep.

It can also reduce your risk of diabetes later in life.

What should I aim for?

Regular activity, such as 30 minutes of walking after lunch or dinner, to improve blood glucose levels.
Try and include muscle strengthening exercise about twice a week, eg. stretches, yoga or swimming.
Try to avoid sitting for long periods of time and try to build exercise into your daily life, such as taking the stairs instead of the lift.

If your blood glucose readings are still above target medications are the next step

Metformin (tablet)

This helps your own insulin to work more effectively, thus reducing some of the insulin resistance associated with pregnancy hormones. It is considered safe in pregnancy. Metformin occasionally may cause side effects (heartburn, nausea, flatulence) but these effects are lessened if you take the tablet with the first mouthful of food as instructed by the doctor.

Insulin (injection)

You may need additional insulin to control your blood glucose levels. This has to be given by injection into the skin. There are different types of insulin regimens and the medical obstetric team will explain which one is best for you.

If you need insulin the Diabetes Specialist Nurse/Midwife will show you how to inject insulin so that you feel safe and confident to do it on your own at home.

Post delivery

Your blood glucose should return to normal post birth. You may need advice from the healthcare team around reducing medications.

Your baby’s blood glucose will need to be monitored post-delivery for a minimum of 24 hours but you may need to stay in hospital longer. This is to check that your baby’s blood glucose is not dropping too low, this is called neonatal hypoglycaemia. Your baby will need to be fed quite soon after delivery and then 3 to 4 hourly, their blood glucose levels will checked regularly before each feed during this time.

Postnatal care

You should be offered a fasting blood glucose test 6 weeks after the delivery of your baby, and a further blood test (called the HbA1c test) 3 months after delivery to check that your blood glucose levels have returned to normal. These tests will be performed at your GP surgery. It is very important that you book this test soon after you have had your baby.

Having gestational diabetes increases your risk of developing diabetes later on in life; therefore it is important to continue to follow a healthy diet and aim to maintain a healthy weight after the birth of your baby. You should have an annual HbA1c to screen for diabetes now you have had gestational diabetes. You are also eligible to take part in the National Diabetes Prevention Programme. Speak with your health care team to see what support is available to you.

Summary:

Check your blood glucose regularly

Regular monitoring of blood glucose helps you and your health care team to ensure you and your baby are staying healthy.

Dietary changes

Control carbohydrate portions – Aim for to fill half your plate with salad and/or vegetables, quarter of your plate with protein and the remaining quarter of your plate with carbohydrate
Aim to eat 20 grams (20g) to 50 grams (50g) carbohydrate per meal
Choose unprocessed, higher fibre carbohydrates and avoid or limit refined carbohydrates.

Stay active

Even a 10 to 15 minute walk before a blood glucose check can help to lower your blood glucose levels.

Take medications as prescribed

Your medical team will monitor you and may suggest medications to help control your blood glucose. It is important you take these medications.

Further Advice

Should you require further advice on the issues contained in this leaflet, or have concerns about your pregnancy, please contact us via telephone:

Labour and Delivery, tel: 01482 604390 and tel: 01482 604490
Antenatal Day Unit, tel: 01482 382729
Antenatal Clinic Reception Desk, tel: 01482 604386
Diabetes Specialist Midwife/Nurse, tel: 01482 675391 or mobile: 07795235929
Diabetes Specialist Dietitian, tel: 01482 675373

You can send your weekly blood glucose readings to the healthcare team at the following email address: hyp-tr.hullgdm@nhs.net