All pregnant people in Aotearoa are offered testing for gestational diabetes in pregnancy, usually between 24-28 weeks.
Gestational diabetes is when your body does not produce enough insulin and you have high blood sugar because of this.
You midwife will offer you an HbA1c (glycated haemoglobin) test as part of your booking blood tests, and the results of this , along with any other risk factors, will determine which test you will be offered.
Risk factors for gestational diabetes include:
- Previous gestational diabetes
- Previous macrosomia (large baby)
- Previous pre-eclampsia
- Previous unexplained stillbirth
- Māori, Pasifika, South-East Asian, or Indian ethnicity
- First-degree relative with diabetes
- BMI >30
- PCOS/PMOS
- Taking steroids or antipsychotics
If your HbA1c in under 42mmol/mol at booking and you have no other risk factors, you will be offered a polycose or glucose challenge test at 24-28 weeks. This test involves going to the lab at a time of your choosing, drinking a solution with 50g of glucose in it, and then having blood drawn one hour after drinking the solution. If the blood glucose reading is under 7.8mmol/L, then no further testing is required. If it is over 11.0mmol/L, then you will be referred to the diabetes in pregnancy team.
If your HbA1c at booking is 42-48mmol/mol, you will be offered an oral glucose tolerance test within a week and again at 24 weeks. If your polycose test is between 7.8-11.0mmol/L, then you will be offered an oral glucose tolerance test.
This test needs to be booked with the lab, and will be first thing in the morning, around 8am. You will need to fast for 8 hours before the test, so from midnight the night before. You will have your blood drawn when you arrive, for a ‘fasting’ value, and then drink a solution containing 75g of glucose. Two hours after the glucose drink, you will have your blood drawn again. If your fasting value is over 5.5mmol/L or your two-hour value is over 9mmol/L, you will be referred to the diabetes in pregnancy team.
If your HbA1c is 48mmol/mol or more at booking, you will be referred to the diabetes in pregnancy team.
Some people do not want to do the polycose or glucose tolerance tests for various reasons, or have trouble doing them due to hyperemesis gravidarum. If this is the case for you, please talk to your midwife, who will advise you.