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Gestational diabetes

Gestational diabetes is the inability to regulate blood sugar during pregnancy and affects around 30,000 pregnancies a year in the UK. It can develop if your body doesn't produce enough insulin and your blood sugar levels get too high during pregnancy. Read on for information on the signs to look out for, and to find out how the condition will be managed by your GP or midwife.

By Mumsnet HQ | Last updated Jun 30, 2021

pregnant woman performing glucose test

What causes diabetes in pregnancy?

Insulin is the hormone that converts blood sugar into energy; when you're pregnant, you need more insulin to help incubate your growing baby and to counteract the insulin-resistant hormones produced by the placenta. If your body isn't able to produce enough insulin, there will be too much sugar in your bloodstream – this is known as gestational diabetes. It can potentially cause problems for you and your baby during and after birth, but the risk can be reduced if it's detected and well managed.

Risk factors for gestational diabetes

You are more likely to develop diabetes in pregnancy if you have any of these risk factors:

  • Being overweight (with a BMI of 30 or more)
  • Already having had a large baby (4.5kg or more)
  • Previously having had gestational diabetes
  • Family history of diabetes (a parent, sibling or child with diabetes)
  • Family heritage with a high prevalence of diabetes (South Asian, Middle Eastern or black Caribbean descent)

Gestational diabetes symptoms

You may not have any symptoms – gestational diabetes is most commonly picked up by routine screening during pregnancy. However, in some cases, you might notice some or all of the following signs:

  • Excessive thirst
  • Weeing a lot
  • Tiredness and fatigue
  • Blurred vision
  • Dry mouth

If sugar is detected in your urine during a routine antenatal check, you'll probably be sent for an oral glucose tolerance test (OGTT).

How the oral glucose tolerance test works

You eat normally in the days leading up to the test. The evening before the test you stop eating before 10pm and don't have anything to eat or drink, except water, until the test the next day. At the clinic, you'll give a blood sample that will be used to measure your blood sugar level after fasting (a baseline test). You'll be asked to drink a very sweet, sugary mixture, then your blood sugar level will be tested again after a two-hour interval and compared with the normal range.

Understanding your test results

You will be diagnosed with gestational diabetes if:

  • Your fasting plasma glucose level (the level of glucose in your first blood test, taken before you'd eaten anything) is 5.6 mmol/litre (millimoles per litre) or above OR
  • Your two-hour plasma glucose level (the level of glucose in your second blood test, taken two hours after you'd had the sugary drink) is 7.8 mmol/litre or above.

You may be told that you are 'borderline' for gestational diabetes. This means that your results are close to the numerical marker of gestational diabetes. Your midwife may repeat the test, and you are likely to be given advice about your diet and exercise.

pregnant woman and doctor

How is gestational diabetes treated?

Treatment for gestational diabetes usually involves making changes to your diet and exercise. Depending on your blood sugar levels when you are diagnosed, you may also be prescribed insulin or medication.

You will be advised by your midwife about your own personal care needs, but these are likely to include monitoring your blood sugar levels at home with a glucose meter.

A glucose meter is a simple test: you prick your finger with the provided lancet, put a tiny drop of blood onto the test strip and then you'll get a numerical reading of the amount of sugar in your blood. Your doctor or midwife will advise you on the right levels for you.

The meter information will help you choose which foods to eat and when, in order to avoid your sugar levels going too low, which is called hypoglycaemia, or too high, known as hyperglycaemia.

You may need to have insulin injections several times a day and record everything you eat. It’s very boring! But the good news is, it nearly always disappears after baby arrives.

What to eat if you have gestational diabetes

Your midwife and healthcare team will be able to advise you according to your specific needs. You may be asked to limit your carbohydrate intake, or stick to slow-releasing carbohydrates, such as oatcakes, to avoid your sugar levels going too high or too low. You may also be told to avoid foods such as juices, sweets and chocolate altogether.

You should bear in mind the general advice surrounding what to avoid eating while pregnant, such as not eating mould-ripened cheeses and part-cooked items such as rare steak, as well as the usual recommendations for a well-balanced diet with lots of protein, such as meat, fish, cheese and nuts, along with vegetables.

This may all sound like a bit of a bum deal, especially as there is so much that you're told you can't eat anyway when you're pregnant. Don't worry, most cases of gestational diabetes resolve after you have given birth, and best of all, you'll have a lovely squishy newborn to cuddle as you resume your pasta habit.

My son definitely wasn't just a 'big' baby – he very much looked like he'd had too much sugar in the womb: massive cheeks, huge chest and stomach, double chin, man boobs. He wasn't especially long and his head circumference was average.

Will gestational diabetes affect my baby?

Most women with gestational diabetes have otherwise normal pregnancies with healthy babies. It can, though, lead to your unborn baby piling on the the pounds – particularly around the shoulders, chest and abdomen (known as macrosomia or 'of large body'). This can make giving birth vaginally a bit more difficult – your baby's large shoulders won't help with what's already a tight squeeze. Very large babies are more likely to be induced and to need delivering by caesarean, though not all babies born to women with gestational diabetes are large.

If your ultrasound scans show that your baby is large (macrosomia), your antenatal team will discuss the pros and cons of a vaginal birth, induced labour and a caesarean section. Any medical intervention comes with risks of its own, so take your time to talk through any questions and come to the decision that feels right for you.

You might also develop polyhydramnios – too much amniotic fluid (the fluid that surrounds the baby) in the womb, which can cause premature labour (in other words, before 37 weeks) or problems at delivery.

There is also a risk you could develop pre-eclampsia, a condition that causes high blood pressure during pregnancy and will need to be treated to avoid complications.

Your baby may also be born with low blood sugar (hypoglycaemia) or yellowing of the skin and eyes (jaundice), both of which may require hospital treatment – but this doesn't mean they have diabetes.

There is a very small risk of stillbirth, but this is rare. According to new guidance from NICE in 2015, if you reach 40 weeks and 6 days before giving birth, then you should be induced, as the risk of stillbirth is increased after this point.

Giving birth when you have gestational diabetes

Most women with gestational diabetes will have a healthy birth. But before you make your birth plan, you may need to take some things into account to make sure you and your baby are safe during and after the birth.

If you have gestational diabetes, you will have less choice about where to deliver your baby. This is because you will need to have your baby in a hospital that can offer 24-hour advanced resuscitation skills.

If you go into labour prematurely (before 37 weeks) you may be given medication to delay the birth – depending on how early you go into labour. You may also be given steroids to help your baby's lungs develop properly. Steroids can raise your blood glucose levels, so if you are taking insulin, you may need to increase the dose or receive insulin in a drip.

How will gestational diabetes affect me after pregnancy?

It's daunting to be told you have gestational diabetes, but there are plenty of Mumsnetters who've been through it before you, and lots of support threads on Mumsnet Talk for sharing experiences and advice.

The good news is that it usually disappears once you've given birth and before then can often be controlled. The less good news is that once you've had gestational diabetes, there's an increased risk you'll develop it in subsequent pregnancies and that you'll develop type 2 diabetes later in life.