Gestational diabetes: risks, diagnosis and treatment

Gestational diabetes (GD) is a form of diabetes that develops during pregnancy (NHS, 2022). It may also be called gestational diabetes mellitus (GDM). It is not the same as pre-existing diabetes.

It is a common complication of pregnancy, currently experienced by around 4 in 10 women and pregnant people who give birth in England (Jabak and Hameed, 2022; NHS England, no date).

In summary (NHS, 2022; NICE, 2020; Jabak & Hameed, 2022):

GD develops when the body doesn’t produce enough insulin for the extra needs of pregnancy. Insulin is a hormone that helps control blood sugar levels.
It can occur at any stage in pregnancy but is more common in the second or third trimester.
GD is normally temporary and usually goes away after birth.
It can lead to problems during pregnancy and after birth for both woman or birthing parent and baby. Early detection and management can reduce these risks.
Some pregnant women and birthing people find the risks can be managed with changes in diet and exercise. Others will also need oral blood glucose (sugar)-lowering tablets or insulin.
Research suggests that pregnant women and people who control GD through their diet and whose babies are growing, normally have a low-risk pregnancy.
Experiencing gestational diabetes increases the chance of developing type-2 diabetes later in life.

How is gestational diabetes diagnosed?

A midwife or GP will ask about risk factors at the first antenatal appointment – around 8 to 12 weeks of pregnancy (NHS, 2022).

Antenatal screening is offered around 24-28 weeks to test blood sugar levels. This is called the oral glucose tolerance test (OGTT) and is for those with risk factors. It takes at least two hours (NHS, 2022).

Women or birthing people who have previously had gestational diabetes will be offered early self-monitoring of blood glucose or an OGTT test as soon as possible after booking (NICE, 2020).

Some women and pregnant people have no risk factors but experience symptoms which may lead the midwife to recommend the OGTT.

If gestational diabetes is diagnosed, a review with the antenatal diabetes clinic will be offered within one week, and the GP or primary healthcare team will be made aware (NICE, 2020).

The pregnant women or person will also be told (NICE, 2020):

What having gestational diabetes will mean for the baby
How good blood glucose control helps the pregnancy and birth
What treatment will involve (a healthy diet and exercise, and possibly medicine)

How does it feel to be diagnosed with gestational diabetes?

Being diagnosed with GD may raise anxiety. Eating a healthy diet or exercising may bring financial worries or conflict with cultural practices for some pregnant women and people. For others, a diagnosis may be seen as an opportunity to make positive lifestyle changes and healthy eating choices (Craig et al, 2020).

As with all decisions about maternity care, the pregnant woman or person is the one who decides which recommendations and offers to accept. Read more in our article about advocacy around birth.

Who is at risk of gestational diabetes?

Some pregnant women and birthing people are more likely to experience gestational diabetes. The risk is higher where (NHS, 2022; NICE 2020):

The Body Mass Index (BMI) was higher than 30 before the pregnancy
They are over 40 years old
They have previously given birth to a baby weighing 4.5kg (10lb) or more
They had gestational diabetes in a previous pregnancy
A parent or sibling has diabetes
Their ethnicity is south Asian, Black, African-Caribbean or Middle Eastern
They have previously had weight-loss surgery

What are the symptoms?

Often gestational diabetes has no obvious symptoms. Most cases are picked up with the OGTT test.

However, some pregnant women and people may develop symptoms if their blood sugar levels get too high, such as (NHS, 2022):

Being more thirsty than usual
A dry mouth
Weeing more often than usual
Tiredness
Blurred eyes
Genital itching or thrush

Some of these can be common symptoms during pregnancy so aren’t necessarily a sign of gestational diabetes.

If these symptoms are experienced during pregnancy or even while not pregnant, speak to a midwife or GP (NHS, 2022).

What is the treatment for gestational diabetes?

Women or birthing people will be offered extra care and support to manage GD and reduce any risks for the baby. This includes additional scans to monitor the baby’s development and amount of amniotic fluid (NHS, 2022; NICE, 2020).

Healthy eating and regular exercise are usually the first steps to control blood sugar levels during pregnancy. Women and pregnant people diagnosed with gestational diabetes will be referred to a dietician and given advice about exercise (NHS, 2022; NICE, 2020).

A blood testing kit will be provided so the woman or pregnant person can monitor their own blood sugar. Some people will be provided with a wearable continuous glucose monitor (CGM) (NHS, 2022).

In some circumstances, the woman or birthing person will be offered medication. This is when (NHS, 2022):

Blood glucose targets are not met after trying regular exercise and eating a healthy diet for a week or two
Blood glucose is very high to start with

Medication will usually be the diabetes drug metformin. In some circumstances, insulin will be offered (NHS, 2022; NICE, 2020).

Can gestational diabetes be prevented?

Research has found that combining changes to diet and exercise might reduce the chance of developing gestational diabetes (Griffith et al, 2020).

The Type-2 diabetes medication metformin may reduce the risk for pregnant women or birthing people with a BMI of 30 or higher (Griffith et al, 2020).

How will gestational diabetes affect pregnancy and the baby?

Most women and birthing people who develop GD have healthy pregnancies and healthy babies (NHS, 2022).

Occasionally, gestational diabetes can lead to (Griffith et al, 2020; NHS, 2022; NICE, 2020):

The baby being larger than usual, which may lead to complications during birth
Too much amniotic fluid around the baby (polyhydramnios)
The baby being born prematurely
Pre-eclampsia
The baby developing jaundice or low blood sugar after birth
Stillbirth – although this is rare.

Gestational diabetes and giving birth

The midwife or GP will discuss the place and timing of birth with the pregnant woman or person (NHS, 2022; NICE, 2020):

Birth will be recommended in hospital to ensure appropriate medical care is available. The pregnant woman or person decides to accept or decline this offer.
Timing will be recommended between 38 and 40 weeks, or earlier if there are concerns about the health of the pregnant woman or person, or baby.
If the baby has not been born by 40 weeks and six days, an induction of labour or caesarean birth will be offered.
Caesarean birth might be advised if the baby is estimated to be very large (macrosomia).
Blood sugar levels will be monitored during and after labour.
The pregnant woman or person will be asked to bring to hospital any medication and the blood sugar testing kit.

Estimates of the baby’s size

While ultrasound estimates of the baby’s weight have improved, the process still depends on the calculation used and the skill of the operator. Research shows that estimates of the baby’s weight may vary by up to plus or minus 10% (Milner & Arezina, 2018). This means that a baby at the higher end of average for a newborn (4kg) could be recorded as 3.6kg (average) or 4.4kg (above average).

What happens after the birth?

In the hours and days after birth where the woman or birthing person has GD (NHS, 2022; NICE, 2020):

The baby needs to be fed within 30 minutes and then at least every two to three hours to help stabilise their blood sugar levels.
The baby’s blood glucose levels will be tested starting 2-4 hours after birth. If they are low, the baby may be fed through a tube or drip until the blood sugar levels are stable. If a baby needs more specialist care, they may be looked after in a neonatal unit.
Any medicine that was being taken by the woman or birthing person to control blood sugar levels is usually stopped.
The mother or birthing person will be advised to keep checking blood sugar levels for one or two days after birth. Another test will be arranged for 6-13 weeks after the birth.
If parent and baby are well, they go home after 24 hours.

What about breastfeeding?

Some parents choose to express and safely store colostrum from week 36 of pregnancy. This colostrum can then be used to supplement feeding a baby after birth (Foudil-Bey et al, 2021).

Expressing colostrum is safe. Some breastfeeding parents who expressed colostrum before birth report feeling more confident with breastfeeding (Foudil-Bey et al, 2021).

Breastfeeding may reduce the risk of developing type 2 diabetes. A review of research has concluded that pregnant women or birthing people with gestational diabetes should be strongly encouraged and supported to breastfeed (Tarrant et al, 2020).

Will gestational diabetes recur or lead to diabetes?

Pregnant women or people who have had GD are more likely to experience it again in a future pregnancy. They will be offered diabetes testing when planning future pregnancies (NICE, 2020).

Up to 1 in 2 women and birthing people who experienced GD in pregnancy go on to develop type 2 diabetes within 5 years (NHS England, no date).

An annual blood glucose test will be offered to anyone who has had gestational diabetes. Even if feeling well it’s important to have the annual test (NHS, 2022; NICE 2020).

The GP can support with guidance to reduce these risks and support if any symptoms of diabetes develop (NHS, 2022; NICE 2020).