Rosie Henley, Registered nurse and midwife in our Health at Hand team

Diabetes in pregnancy


26 February 2021

Approximately 16 in every 100 women giving birth the UK will develop gestational diabetes (Diabetes UK, 2021). 

Gestational diabetes

This is a type of diabetes that develops in pregnancy usually in the third trimester after 28 weeks gestation.

For those with the condition in the first trimester it’s likely they had pre-existing high glucose levels before pregnancy.


Hormones such as oestrogen, progesterone and human placental lactogen which are produced during pregnancy can cause the body to be insulin resistant. This means that cells in the body don’t respond as well to insulin and glucose levels in the blood remain high. This effect enables the extra glucose and nutrients to pass to the unborn baby for growth.

The body would usually produce more insulin to cope with the increased amount of glucose in the blood. But, in pregnancy some women don’t produce enough insulin or they’re more resistant to insulin. These women would then have gestational diabetes.

Risk factors and diagnosis

The risk of developing the disease may increase with the following:

  • Being overweight with a body mass index (BMI) above 30
  • Previous birth of a large baby (weighing 4.5 kg or more)
  • A history of gestational diabetes
  • Close family history - a parent, brother or sister with diabetes
  • Family origin is South Asian, black Caribbean or Middle Eastern (these groups have a higher risk of developing gestational diabetes).[1] 

These risks factors are taken into consideration when planning antenatal care and screening.


Gestational diabetes is often found during routine screening as you may not be aware of any symptoms.

But in some cases, the following symptoms develop due to high blood glucose levels:

  • Dry mouth and being thirsty
  • Needing to pass urine frequently
  • Feeling tired and blurred vision
  • Recurrent infections, such as thrush.

If any of these symptoms or risk factors are present, a test for gestational diabetes will be offered.

The oral glucose tolerance test (OGTT) can be used to test for gestational diabetes. This blood test is usually performed at 24 to 28 weeks of pregnancy, blood is taken before breakfast and again two hours later following a glucose drink. This will show how the body is managing the glucose.

Those who’ve had gestational diabetes before are offered this test at 16-18 weeks followed by a repeat test at 28 weeks if the first test was normal.

Possible complications associated with diabetes during pregnancy

Most women who have diabetes or develop diabetes in pregnancy have healthy pregnancies and healthy babies. But serious complications can occur for mother and baby, therefore it’s important to have well controlled blood glucose levels before and during pregnancy to help reduce the following risks:

  • Baby being born before 37 weeks (a premature birth).
  • Increased risk of miscarriage or the baby dying late in the pregnancy (stillborn).
  • Macrosomia, a larger than average baby, for example 4kg (8.8lbs) or more. In response to the excess glucose in the mother’s blood passing to the baby, the baby produces insulin, enabling the glucose to enter the cells and the baby grows. This may lead to problems around birth and delivery for example, induction of labour, caesarean section or shoulder dystocia. Shoulder dystocia is an obstetric emergency where there is a need for additional obstetric manoeuvres to deliver the baby after the head has delivered and gentle traction has failed.
  • Congenital abnormalities.
  • Possible increase in infections during the pregnancy and with potential that the infections may be severe.
  • Low blood glucose (hypoglycaemia) following birth.
  • Risk of long-term diabetes complications becoming worse, including problems with your eyes (diabetic retinopathy) and problems with the kidneys (diabetic nephropathy).

Management of diabetes in pregnancy

It’s important to have good preconceptual care especially if already diabetic. For those overweight it’s advised that they try and lose weight and understand the importance of a healthy diet and active lifestyle. Before becoming pregnant women should talk with their doctor or diabetic nurse specialist to understand the possible risks and how to reduce these risks and have a healthy pregnancy. For those with diabetes it may be more difficult to recognise when blood glucose levels are low, and advice will be needed on best management of glucose levels to avoid hypoglycaemia.

This may involve regular testing of blood glucose levels and ensuring they remain within an ideal blood glucose level manageable for the woman concerned. For those with existing diabetes an HbA1c test should be offered to assess blood glucose levels over the past months. Levels should be below 6.1% before becoming pregnant. Risks to baby are then reduced.

Folic acid supplements are recommended while trying for a baby and in the first 12 weeks of pregnancy. This helps reduce the risk of birth defects such as spina bifida.

For those with type 1 diabetes, blood glucose levels need to be checked by testing their blood.

Gestational diabetes usually doesn’t need diabetes medications and can be managed through healthy diet and activity. A referral to a dietician is usually arranged.

For those with type 2 diabetes and already taking medications, any changes will be managed by the diabetologist or nurse who may suggest some changes before becoming pregnant or may discuss the possibility of starting insulin injections.

Diabetes increases the chance of conditions such as diabetic retinopathy and diabetic nephropathy which can deteriorate further during pregnancy. So, screening of the eyes and kidneys is performed before and during pregnancy to check for any deterioration.

Screening and monitoring of the foetus

Extra antenatal checks along with the usual antenatal care may be offered.

There’ll be a dating and screening ultrasound scan at the end of the first trimester and between 18-20 weeks. This is then followed up with the offer of a scan to check foetal growth and the volume of amniotic fluid every four weeks from 28–36 weeks. Then weekly antenatal checks from 38 weeks.

Labour and birth

Due to the potential complications and risks already highlighted, it’s strongly recommended that labour and birth is supported by a consultant-led maternity team in a hospital. During labour, closer monitoring of blood glucose levels is needed and it may be that an intravenous drip of insulin as well as glucose is needed, to enable careful control of blood glucose levels.

For some women, their medical team may suggest an induction of labour before 40 weeks gestation or even a caesarean section delivery. 

After birth

For those who have gestational diabetes, blood glucose levels usually return to normal once the baby is born and any medication is usually stopped. Blood tests are taken before discharge to make sure this has happened with a follow up fasting blood test at the six-week postnatal check. 

For those with type 1 or 2 diabetes, readjustment of medication or insulin is needed with eventual return of pre pregnancy treatment levels. Blood glucose levels need to be well controlled and it may be that some change in the diabetes treatment is needed.

Mothers are encouraged to feed their babies as soon as possible after birth and the babies' blood glucose levels are checked to ensure they are stable. For those that are experiencing unstable blood sugar levels, extra care may be required in a neonatal unit.

As with all new mums, breastfeeding is encouraged and harvesting of colostrum may be suggested during pregnancy to assist with feeding in the early days if mothers prefer not to give formula milk.

Those who’ve had gestational diabetes have an increased likelihood of developing gestational diabetes in future pregnancies and also type 2 diabetes.

Further reading

Diabetes hub - AXA Health

Pregnancy hub - AXA Health

How to get the birth you want - AXA Health


[1] NICE Clinical Guidelines: Diabetes in pregnancy: Management of diabetes and its complications from pre-conception to the postnatal period. Last updated 16 December 2020 (Accessed 3 March 2021)

Diabetes UK

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