Gestational diabetes – diabetes that develops during pregnancy | Mate huka i te hapūtanga

Gestational diabetes (mate huka i te hapūtanga) is when a pregnant woman who was not known to have diabetes before pregnancy develops high blood glucose levels during pregnancy.

undefinedIt is different from pre-existing diabetes and pregnancy, which is when you have diabetes (type 1 or type 2 diabetes) before you get pregnant.

Gestational diabetes affects about 4%–8% of all pregnant women. Untreated, it can lead to problems for both mother and baby. Treatment includes healthy eating and exercise, and possibly use of insulin.

Gestational diabetes usually goes away after your baby is born; however, it can recur in future pregnancies and it is important to know you are at higher risk of developing diabetes in later years.

Gestational diabetes explained

(Cathy Moulton, a Diabetes UK care adviser and Kimberley's experience, NHS Choices)

Who is at higher risk of gestational diabetes?

Some women are at high risk of developing this condition. The risk factors include:

  • overweight/obesity
  • excessive weight gain in pregnancy
  • family history of diabetes
  • over 30 years of age
  • previous history of gestational diabetes
  • poor obstetric history – unexplained stillbirth, miscarriage
  • previous large baby or babies
  • ethnicity (some women from certain ethnic backgrounds are at higher risk)
  • polycystic ovarian syndrome.

Gestational diabetes can also occur in women who have none of these risk factors. Women with gestational diabetes in an earlier pregnancy should be tested as soon as a new pregnancy occurs.

How is gestational diabetes detected?

Every pregnant woman should now be offered a blood test for glycated haemoglobin (HbA1c), as a routine part of booking antenatal blood tests before 20 weeks. This will help identify women with probable undiagnosed diabetes or prediabetes and will help to identify women at high risk of developing gestational diabetes.

At 24–28 weeks of pregnancy, you will be offered a further blood test to check for any diabetes. 

  • For women whose earlier HbA1c was 41–49 mmol/mol at booking, a two-hour glucose tolerance test (GTT) is organised. 
  • For women whose HbA1c was normal, a one-hour, 50 g oral glucose challenge test (polycose) is done. 

What are the complications associated with gestational diabetes?

During the pregnancy

  • Untreated, the high sugar (and fat) in the blood of a woman with gestational diabetes can overfeed the baby while it is in the womb, leading to "macrosomia" or a "fat baby".
  • Premature birth (baby being born before 37 weeks) is more common.
  • Miscarriage (before 23 weeks) and stillbirth rates (baby dying before birth) are also higher.


  • Large babies lead to higher rates of difficult births, a need for surgical (caesarean section) or assisted delivery. 
  • Shoulder dystocia is a serious complication when the baby’s head passes through the vagina, but their shoulder gets stuck behind the mother's pelvic bone (the hips and ring of bone that supports your upper body). When this happens, both mum and baby are at risk of serious injury. 

After birth

  • Babies can suffer from low blood sugar within the first day or two and need closer monitoring.
  • Breathing problems are also more common shortly after birth.

Late effects

  • Babies are at increased risk of developing diabetes or obesity (having a body mass index of more than 30) later in life.
  • Women who have had gestational diabetes are also at much higher risk of developing diabetes in the future. 

What is the treatment for gestational diabetes?

Treatment is started as soon as gestational diabetes is diagnosed. The aim is to keep blood glucose levels in the normal range (equal to those of pregnant women who do not have gestational diabetes). 

Treatment includes eating a healthy diet and being active every day, aiming for 30 or more minutes a day. If this doesn't keep the blood sugars within the target range, then metformin and or insulin may be added. Your care will be provided in consultation (including virtual clinics) with an obstetrician, a physician and a dietician as well as by your lead maternity carer (LMC). Read more about taking metformin for gestational diabetes

Following the treatment advice increases the chances of a healthy pregnancy and birth, and helps your baby avoid future health problems. It will also help avoid the complications listed above. 

Read more about gestational diabetes & treatment Auckland District Health Board.

Looking ahead

Gestational diabetes usually goes away after pregnancy. You should have a blood test at 3 months after delivery to check. For 20-30% of women it doesn't and permanent diabetes can occur.

  • If normal, then you should make sure you have a HbA1c test each year to screen for new onset of diabetes.
  • In a few women, pregnancy uncovers type 1 diabetes diabetes. These women will need to continue diabetes treatment after pregnancy.

Knowing you have an increased risk of type 2 diabetes means you can take steps towards trying to prevent it by:

  • controlling your body weight
  • making healthy food choices
  • taking regular exercise.

Learn more

Gestational diabetes Diabetes NZ
Introduction to gestational diabetes NHS Choices, UK


Screening, diagnosis and management of gestational diabetes in NZ – a clinical practice guideline. Ministry of Health, NZ, 2014
Māori health literacy research – gestational diabetes mellitus Workbase Education Trust, NZ, 2014

Credits: Latest update by Health Navigator team March 2017.