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Diabetes testing in pregnancy

Diabetes can cause problems for you and your pēpi during your pregnancy and birth. It is important to know if you have diabetes, or if you are at risk of developing it. Find out about testing and how to look after yourself and your pēpi.

Diabetes in pregnancy

When we eat, a hormone called insulin helps move sugar from our food through our blood and into our muscles. It then turns into energy to help us move. 

When you are pregnant, your body produces lots of other hormones to help your pēpi grow. Some of these hormones can stop insulin working well. This causes sugar to build up in your blood because it cannot get to your muscles. You have diabetes when you have too much sugar in your blood.

Pregnancy diabetes generally goes away after your pēpi is born. But it leaves you with more chance of developing diabetes again later in life.

Risks if you have diabetes in pregnancy

If you have diabetes when you are pregnant and do not get treatment:

  • your pēpi can grow too big, and this can cause problems for you and your pēpi during the birth
  • you can develop high blood pressure and preeclampsia
  • your pēpi may have problems with their own blood sugar when they are born
  • your pēpi will have more risk of getting diabetes later in life.
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  • The HbA1c is a simple blood test. This is offered at the same time as your first antenatal blood tests. You can eat and drink before the test, and leave when it is done.

    The HbA1c test shows your average blood sugar level for the past 4 to 6 weeks. It measures what percentage of your haemoglobin is coated with sugar. Haemoglobin is the protein in your red blood cells that carries oxygen. A high HbA1c level means that:

    • more sugar has been circulating in your body
    • you have a higher risk of getting diabetes in your pregnancy.

    If the HbA1c test shows that you have diabetes

    You will be offered another HbA1c test 3 months after your pēpi is born. This test is to check that your blood sugar level is back to normal.

  • If you are not at high risk of diabetes in pregnancy, your midwife or doctor will offer you an oral glucose challenge test (also called a polycose test). This test is done when you are between 24 and 28 weeks pregnant. This test measures how well your body can process sugar. You can have this test at any time of the day.

    For this test, you will drink a sugary drink and then wait 1 hour before giving a blood sample. You will not need to do anything special before or after the test. Most people do not have side effects from the oral glucose challenge test.

  • If your HbA1c or oral glucose challenge test results were high, your midwife or doctor will offer you an oral glucose tolerance test. This test will confirm if you have pregnancy diabetes or not.

    This test is done on an empty stomach, so your appointment for the test will be in the morning. You should not eat or drink anything for at least 8 hours before the test. You can eat the day before the test. But do not have anything to eat or drink (except water) after your last meal the evening before.

    When you arrive for the test, a blood sample is taken to measure how much sugar is in your blood after you have been fasting. Next, you will drink a sugary drink and then wait 2 hours before giving another blood sample. You will not be able to leave the lab for 2 hours.

    Most people do not have side effects from the OGTT. Some people feel sick, sweaty or light-headed after they drink the sugary drink. But long-term, serious side effects from this test are very uncommon.

    If the tests show that you have diabetes, your midwife or doctor will talk to you about ways you can access care to manage it. They will also refer you to a specialist for advice.

Keep you and your pēpi healthy

Keep doing these things to keep you and pēpi healthy during your pregnancy:

  • attend regular check-ups with your midwife
  • get regular exercise
  • eat healthy food
  • do not smoke
  • do not drink alcohol
  • avoid drugs.

For more information about the tests

  • Talk to your midwife, doctor, diabetes nurse or specialist.
  • Visit the Ministry of Health National Maternity Guidance web page.
  • Visit the Diabetes New Zealand website.

Diabetes New Zealand website (external link)

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