Gestational Diabetes
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Thomas Bamford
I am doctor in Obstetrics and Gynaecology, I started working as a doctor in London and then moved to Manchester more recently to complete my specialty training. I have an interest in finding innovative ways to improve the care of women both during the antenatal period but also during childbirth. Working within this field is an incredible privilege and I find it very rewarding.
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Maintaining a healthy weight in pregnancy

Gestational Diabetes

Gestational Diabetes affects up to 5% of pregnant women, usually in the second or third trimester. The number of women being diagnosed with gestational diabetes is increasing over recent years. In the vast majority of cases it is temporary and goes away after your baby is born. If you already have type 1 or 2 diabetes then not all aspects of this article are relevant for your care however you may find some of the information useful.
In Short
Gestational diabetes is caused by the increase of certain pregnancy hormones, which reduce the effectiveness of insulin. Insulin is a hormone produced by our body to enable the sugar (glucose) in our blood to be converted to energy. In women with gestational diabetes the pancreas (an organ that produces insulin) cannot meet the demands of the body and so glucose levels rise. It is this high level of glucosethat if left uncontrolledcan lead to complications both for your delivery and for your baby.

In some situations it isn’t clear why a certain woman has developed gestational diabetes, however you are more likely to have it if you:1,2

  • Are overweight
  • Have a family history of diabetes
  • Are of South Asian, Afro-Caribbean, or Middle Eastern Background
  • Had a previous large baby (over 4.5kg)
  • Have Polycystic Ovary Syndrome (PCOS)
  • Had Gestational Diabetes before

Gestational Diabetes doesn’t usually cause you to have any symptoms, and is usually just picked up on a blood test (see below). If it does cause any symptoms the ones to watch out for are:

  • Increased thirst
  • Needing to pee more than usual
  • A dry mouth
  • Tiredness

Remember that some of these symptoms are common for all pregnancies anyway, but if you’re worried, speak to your midwife.

The Diagnosis

Should I be tested for Gestational Diabetes?

Not everyone is routinely tested for gestational diabetes. The National Institute of Clinical Excellence (NICE) recommends that women with any of the following risk factors are tested:1

  • Body mass index of 30 or above
  • Previous big baby (weighing 4.5kg or more)
  • Previous gestational diabetes
  • Family history of diabetes (first degree relative with diabetes i.e. parent or sibling)
  • If you are of South Asian/Middle Eastern descent or of African/African-Caribbean origin. This is because we know these groups of women are up to 6 times more likely to develop gestational diabetes

Your midwife will book you in for this test if you meet the criteria at your booking visit. If you have had gestational diabetes before this test is done sooner.

Gestational Diabetes is usually tested for using the Oral Glucose Tolerance Test (OGTT)between 24 and 28 weeks. It is basically testing your body’s ability to process sugar and maintain a normal blood sugar level. There is no riskto you or your baby when undertaking this test. Instead, some hospitals will test you at your booking appointment with a fasting sugar blood test if you are high risk, and then again at 24 weeks.

How to prepare for the glucose tolerance test

Leading up to the test continue to eat your normal diet until the night before. From 10pm the night before you should only have plain water; this means no food including mints, chewing gum, and medication for heart burn (as this can effect the outcome).

When you come for your appointment you will have a blood sample taken and then you’ll be given a special sugary drink to take. After two hours the blood test will be repeated; you mustn’t eat anything else between the two blood tests.

Following the second blood test you can go back to eating and drinking as you would normally. The results of the test are usually available by the following week. If the test is abnormal you will be contacted to discuss this with a Diabetes Specialist Midwife and further appointments will be made for you to see a consultant. See below for an idea of how we monitor you throughout your pregnancy and to get an idea of the frequency of the appointments.

We know that a diagnosis of gestational diabetes can be a disappointment or a shock. Remember your obstetric team want the best for you and your baby, and it is important to understand the risks in order to understand why all the extra appointments are necessary. If we get good control of your diabetes early on you are more likely to have a normal delivery.

What are the risks of having Gestational Diabetes?

Good management of your diabetes will reduce these risks to you and your baby. Some of the risks sound scary but it is important you are well informed about what could happen. Your team will make every effort to reduce these risks and this is why we take it so seriously. Most women with gestational diabetes go on to have healthy pregnancies and healthy babies.

The risks of having gestational diabetes are:

  • Large Baby (Macrosomia): Due to the high sugar levels your baby can grow bigger than normal, this can lead to problems during delivery such as:

  • Trauma/tears: reported rates of tears vary between units (but happen in approximately 2-6% of all women in the UK)3

  • Instrumental Delivery: The need for forceps (an instrument put around baby’s head to help deliver) or ventose (a suction cup applied to the baby’s head) to assist with delivery. The overall rates of this are between 10 and 13% for all women in the UK, in the vast majority of cases this has no long term consequences for your baby.4

  • Your baby’s shoulders getting stuck during delivery (shoulder dystocia): this requires manoeuvres by your midwife and/or doctor such as applying pressure to your tummy or pushing your legs onto your chest. Fortunately this is one of the less common complications; studies involving the largest numbers of vaginal deliveries report it to occur in approximately 0.6%5.

  • Low blood sugar of your baby after delivery (neonatal hypoglycaemia): If your blood sugar is high, your baby will adapt to the high sugar environment by producing more insulin. Once delivered this high level of insulin may cause your baby’s blood sugar to drop (hypoglycaemia). Your baby’s blood sugar will be tested soon after birth and treated if low. This will eventually correct itself with time but in some cases your baby may need more support on the Neonatal Intensive Care Unit (NICU).

  • High blood pressure: Women with gestational diabetes are statistically more likely to have problems with having higher blood pressure.

  • Pre-eclampsia: this is a particularly serious condition that causes high blood pressure during your pregnancy. Although Gestational Diabetes doesn’t cause pre-eclampsia, we know that you are more likely to get it if you have gestational diabetes and so it is important to know what symptoms to look out for:
  1. Headaches
  2. Visual changes (e.g. flashing lights)
  3. Pain in tummy and ribs
  4. Dizziness

  • Premature delivery (early birth i.e. at less than 37 weeks): We know that the risk of pre-term delivery is higher overall.
  1. This risk is higher if you were diagnosed with gestational diabetes before the 24th week, the risk goes down the later you are diagnosed.
  2. This risk is often due to these women developing some of the other complications mentioned such as pre-eclampsia rather than the diabetes alone.

  • Induced labour (starting off artificially). There are some situations where this is recommended; the main one is if you require medication to control your diabetes. Most hospitals recommend induction from 39 weeks- see below.

  • Less likely to have a water birth and more likely to deliver on the labour ward.

  • Having to have a Caesarean section: The caesarean section rate nationally is approximately 28% for both elective and emergency deliveries.6Some studies have shown that this is increased in women with gestational diabetes. However, this may be for a variety of reasons including patient choice, fetal distress, or progressing slowly in labour. The vast majority of women have normal vaginal deliveries. If your body mass index is more than 35, you will be7 more likely to have a caesarean section during your labour because either you or your baby are not coping with the labour. If you are overweight and this is your first baby, you are more likely to have an urgent caesarean section to have major blood loss compared to mums with a healthy BMI.

  • Increased risk of developing gestational diabetes in future pregnancies: Once diagnosed with gestational diabetes, women are estimated to be seven times as likely as those without the condition to develop Type 2 Diabetes later in life. The lifetime risk of developing Type 2 Diabetes after gestational diabetes is at least 7%.8 We therefore ask your GP to regularly test your HbA1c (a blood test that shows your average sugar control over the last few months). This is done 6 weeks after delivery and then annually.

  • Still birth: This is obviously the scariest risk and worst possible outcome, but we know that there is a very slight increase of stillbirth towards the end of pregnancy when compared to women without gestational diabetes. In the UK, we are fortunate enough to live in a country where we know that the care you receive reduces the risk of stillbirth by four fold when compared to developing areas of the world.

The Management of Gestational Diabetes

Once you have a diagnosis of gestational diabetes you will have additional appointments, usually first with doctors and then more regular appointments with a diabetes specialist midwife and if necessary further doctor appointments. You will also be offered an appointment with a dietician.

The first and most important step to managing gestational diabetes and controlling your sugar is with diet and lifestyle changes. Many women find that this is all it takes in order to get their sugar levels under control.


The carbohydrates we eat are converted into glucose (sugar), and the rate at which this conversion happens varies depending on the type of carbohydrate eaten. It is important to be aware of how much glucose the food you are eating contains to avoid raising your blood sugar too quickly. There are two forms of carbohydrate:

  • Sugary Carbohydrate- such as that found in sweets, soft drinks, fruit, cakes. This kind is quickly converted to glucose, which causes a sharp rise in your blood sugar.
  • Starchy Carbohydrate- such as that found in rice, flour, and potatoes is converted at a slower rate and release over a longer period of time, leading to more stable blood sugars.


Slows down the conversion of carbohydrate to glucose, therefore eating more brown rice or wholemeal/brown pasta can help.


A small amount of fat is good for you as it also slows down the conversion of carbohydrate to sugar

Glycaemic Index

Glycaemic index (GI) is a way of scoring food 1-100 according to how they affect your blood glucose. Foods with a high glycaemic index such as potatoes and white bread lead to quick release of sugar and high sugar levels, whereas bran products (e.g. broccoli, brown bread) have a low GI and will raise blood sugar more slowly. The Diabetes UK website has some good information about what types of food fall into which category.

Diabetes UK


Everyone knows about the sugar in sweets and fizzy drinks, however even healthy food options such as yoghurts and fruits contain sugar. The daily recommended intake of sugar will be different for people of different heights, weights, and ethnic background. For a 2,000-calorie diet, a total sugar intake of 90g, or 24 sugar cubes, is recommended. This includes natural sugars, such as those in rice, milk, and fruit. Added or artificial sugars, such as sweets and fizzy drinks, should only make up about 5% of your diet. This means you should be aiming for a total of 25g or the equivalent of 6 sugar cubes per day of added sugars.

Click here for more information on healthy swaps:

Healthy Swaps

Click here to find out more about Sugarsmart:




  • Try to avoid sugary drinks such as fizzy drinks and fruit juice, and replace these instead with water. You can try adding fruit or herbs to water for flavour.
  • Avoid putting sugar in teas or coffees

Food Swaps

  • Choose breakfast cereals with little sugar
  • Use low sugar alternatives, eg semi-skimmed milk, plain or low sugar yoghurt. Try adding nuts and seeds or spices such as cinnamon to plain yoghurt for flavour.
  • Swap white bread for wholemeal options, such as wholeweat flour in rotis and chapattis.
  • Choose brown basmati rice instead of pilau or fried rice.
  • Cook with unsaturated oils such as sunflower, olive, or rapeseed instead of butter or ghee
  • Grill or bake foods instead of frying.
  • Make your own sauces rather than buying ready made ones
  • Try vegetable alternatives to carbohydrates, eg courgette spaghetti, cauliflower rice, or butternut squash chips
  • Hummous and vegetable sticks
  • Nuts
  • Apple and Nut Butter
  • Plain popcorn
  • Beware of ‘healthy’ snacks; dried fruit and honey are better than artificial sugar, but still contain sugar
  • Beware of low-fat options that may be full of sugar
  • Eat regularly. Some people find eating small meals but more regularly helps to keep their blood sugar in a healthy range.
  • Plan your meals in advance
  • Watch portion sizes
  • Carry healthy snacks with you
  • Think of sugar as a treat
  • Learn what works for you
  • Stay hydrated


One way to lower blood sugar levels is to exercise. When we exercise out muscles take in glucose and our muscles remain more sensitive to insulin for some time. The end result is lower blood glucose levels. Aiming for 30 minutes of moderate physical activity per day can make a big difference. It is important that the exercise isn’t too strenuous, but you should aim for exercise that makes you slightly out of breath with a faster heart rate.


You will be shown how to test your blood glucose level by you team. Here is a summary of the steps:

  1. Wash your hands
  2. Set up the finger pricker with a clean needle
  3. Insert a test strip into the metre
  4. Use the pricker to prick the side of your finger
  5. Place a spot of blood onto the end of the testing strip that is sticking out of the metre
  6. After a few second the machine will display your sugar level
  7. Clean the blood off your finger and record your results
  8. Dispose safely of the needle

You will be asked to do this at least twice a day, at the start it is helpful to test more often so we can assess when during the day your sugar levels are high. A dietician can then discuss with you what exactly it might be that you need to avoid eating and suggest some alternatives.

  • Before breakfast (this level should be 5.3 or lower) ‘fasting glucose’
  • 1 hour after meals (this level should be 7.8 or lower). Some hospitals recommend testing before meals instead of after, this will be discussed with you at your consultation.

For example it would be ideal to test before breakfast, 1 hour after lunch and 1 hour after dinner for the first few days. And then once a trend is established this can be reduced to twice a day, switching the times you test.


Once you have met with the doctors and the dietician you will often be given a period of time to try and make these changes as best you can. You will then be seen again where the doctors or specialist midwife will look at your blood glucose results to see if the changes have made a difference. In some cases it is necessary to start a medication to help control blood glucose if lots of your readings are still high. These medications have been proven to have no damaging effects for you or your baby.

The medication used is called Metformin, taken up to three times a day. It works by helping your body use the insulin it has and reducing your body’s resistance to insulin. The most common side effects of metformin are some stomach cramps, feelings sick, vomiting, and diarrhoea. The side effects can be reduced by taking the tablet with a meal, or shortly after eating. Metformin is often started at a low dose, which gives your body time to get used to the medication. If, however, the side effects don’t improve or become a problem it is important to speak to your midwife or doctor as there are alternatives. It is also important to remember that not everyone will get side effects and this is just something to be aware of.


Most women with gestational diabetes can be managed with diet and metformin alone. In approximately 20% of patients Metformin doesn’t give the adequate control we would like and so we have to consider using Insulin.

You will need to learn how to give yourself insulin injections, and your midwife will show you how to do this. We know the prospect of lots of injections can seem daunting but don’t be put off. The needles used to give insulin are very different from injections you will have been given in the past; they are very fine and the insulin doesn’t need to be given very deep underneath the skin.

How much insulin you will need and how often will be tailored to you by your diabetes team.


Around 37 weeks onwards your obstetric team will talk to you about a plan for your delivery. This is tailored to each person depending on your sugar control.

In general if your gestational diabetes is controlled by diet alone and if you have no other risk factors it will be recommended that you deliver by 41 weeks.

If you have any other problems or are on Metformin or Insulin, most hospitals will recommend that you deliver by 39-40 weeks.

If you have not gone into labour by these points, induction of labour will be recommended. The main reason for induction is to prevent stillbirth and reduce the chances of the complications mentioned above.

Most women with gestational diabetes have a normal delivery, but it is important you take into consideration the following before you bake a plan for your birth:

  • You will be advised to give birth in hospital
  • In most hospitals, if you are on medications or insulin to control your diabetes you won’t be able to deliver on the birthing centre. If your gestational diabetes is controlled by diet alone this is usually possible as long as there are no other factors which make your delivery high risk. Because of the higher rates of complications it is important you are in an environment where the right people and resources are around to help should they occur.
  • Your blood glucose level will need to be monitored hourly during labour to ensure it stays within safe levels. We may need to give you insulin or glucose during delivery should they go out of range. Usually if you are diet controlled we don’t have to monitor you so intensively throughout.

All the obstetric team of doctors and midwives will want you to have the birth you hoped for but it is important to remember that things don’t always go to plan. The safety of you and your baby is the most important thing.

Induction of Labour

Induction involves starting labour off artificially. You can find out more information on this by clicking here.

Caesarean Section

A Caesarean section (commonly known as a C-section) is not recommended for Gestational Diabetes alone. It is only if there are other factors such as changes to your baby’s growth, or if you develop other complications that it might be recommended. There is currently no evidence that Caesarean sections for the sole reason of having a big baby has any benefits and so is not recommended by most Obstetricians. The doctors will take into consideration your wishes for your birth and no one will force you to do anything. A Caesarean section is a big operation with risks such as bleeding (1 in 200), infection (6%), clots in legs and lungs, and damage to surrounding organs (e.g. Bladder injury 1 in 1000). Therefore, this will only be recommended if the benefits will outweigh these risks.


Booking at 10 weeks: Baseline blood test, HbA1c (a blood test which looks at your overall control; if you have had gestational diabetes in a previous pregnancy you will be offered the Oral Glucose Tolerance Test earlier in your pregnancy)

Offered combined screening/Quadruple test

20 week: Anomaly Scan – detailed scan which can pick up abnormalities in the baby

You will usually have scans 3-4 weekly until term

24 weeks: Oral Glucose Tolerance Test if high risk

Once you have been diagnosed with gestational diabetes the specialist midwife will usually see you or have a phone consultation every 1-2 weeks depending on your control.

28 weeks: Repeat blood test to check for anaemia and to group your blood. Ultrasound scan of Fetal growth and Amniotic Fluid Volume (the amount of fluid around the baby). You will usually see the doctors after this.

32 weeks: HbA1c, Ultrasound scan of Fetal growth and Amniotic Fluid Volume. You will usually see the doctors after this.

34 weeks: FBC (blood test)

36-7 weeks: HbA1c, USS Fetal growth and Amniotic Fluid Volume. You will usually see the doctors after this.

37-39 weeks: Decision to be made about delivery

6 weeks postnatal after delivery: HbA1c by your GP

  1. NICE. Diabetes in Pregnancy: management from preconception to the postnatal period. NICE guidelines. 25thFeb 2015.
  2. RCOG. Gestational Diabetes Information for You. Patient Leaflet. March 2013
  3. Thiagamoorthy, G., Johnson, A., Thakar, R. et al. National survey of perianal trauma and its subsequent management in the United Kington. Int Urogynecol J (2014) 25: 1621.
  4. RCOG. Operative Vaginal Delivery. Green-top guideline No 26. January 2011.
  5. RCOG. Shoulder Dystocia. Green-top guideline No 42. March 2012.
  6. NHS Maternity Statistics, England 2016-2017.
  7. Tommy’s. C-section advice for overweight women. Available at:
  8. Diabetes UK. Facts and Stats. March 2015. Available at:
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This article is for information only and should not be used for the diagnosis or treatment of medical conditions. Essential Parent has used all reasonable care in compiling the information from leading experts and institutions but makes no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details click here.