Pre-existing diabetes and pregnancy

Having high blood glucose levels because of type 1 or type 2 diabetes can affect all stages of pregnancy, from conception to delivery. But, if you maintain healthy blood glucose levels before and during your pregnancy, you have the same chance of delivering a healthy baby as all other women.

What is pre-existing diabetes?

Diabetes is a condition in which your body has too much sugar (called glucose) in the blood. Pre-existing diabetes means you have diabetes (type 1 or type 2 diabetes) before you get pregnant. This is different from gestational diabetes which is a kind of diabetes that some women get during pregnancy.

Can having diabetes affect pregnancy?

If untreated, diabetes can cause problems for both mum and baby.

Risks to your health:

  • Labour may start too early (premature labour).
  • May develop high blood pressure and preeclampsia.
  • Increased risk of gum disease, bladder and other infections.
  • Worsening of any problems caused by diabetes such as eye, kidney, heart or nerve problems.

Risks to your baby's health:

  • Miscarriage or stillbirth.
  • Very large in size at birth, which may cause problems during birth.
  • Jaundice (yellow skin and eyes).
  • Birth defects such as some heart defects.
  • Obesity later in life.

Planning your pregnancy

If you have type 1 or type 2 diabetes, try to plan your pregnancy as much as possible, to get your body ready before you are pregnant. This is important because your baby's organs start forming in the first 6 to 8 weeks after conception. Here's what you can do:

  • Let your healthcare provider know you are planning a pregnancy about 3 to 6 months beforehand.
  • Closely monitor your blood glucose levels and work towards having good blood glucose control. 
  • You may be advised to use contraception and delay getting pregnant until your blood glucose is well controlled.
  • Start taking folic acid supplements. Lack of folic acid has been linked with birth defects called neural tube defects. Folic acid is thought to reduce the risk of you having a child with spina bifida or other abnormalities. 
  • Your healthcare team will review your medications. If you are taking a sulphonylurea, this is likely to be stopped and replaced with insulin.

Other things you can do:

  • Eat healthy food and stay active.
  • Aim for a healthy body weight.
  • Avoid alcohol, smoking and recreational drugs.
  • Make sure your vaccinations are up to date.

Not everybody can plan their pregnancy. If you have diabetes and think you might be pregnant, see your doctor as soon as you can. 

During pregnancy

During pregnancy, you will be cared for by a specialist diabetes and obstetrics team during your pregnancy. The team is likely to include a diabetes specialist, an obstetrician, a midwife or specialist diabetes midwife, a dietitian and a diabetes nurse educator.

  • You will need to test your blood glucose levels very often during your pregnancy. Most people test between 4 to 8 times a day during pregnancy. You will also be asked to get frequent laboratory blood glucose and HBA1c levels during pregnancy. These are to back up the results you are getting on your own blood glucose meter. 
  • Depending on your blood glucose levels, you may be started on insulin. You will receive support and education about insulin from the diabetes midwife or diabetes nurse educator. 
  • You are likely to have frequent scans during your pregnancy.Scans are a good way of checking on the babies growth and development. They can also pick up on any problems developing. 

During labour and delivery

You should plan the birth together with your doctor and midwife. You may be advised to have a caesarian delivery. Women with diabetes have a higher chance of needing a caesarian section than women without diabetes. Also, labour may need to be induced if your baby is becoming large or your pregnancy is going over term (beyond 40 weeks).

You might be advised to have a drip in with glucose and insulin while in labour. The rates of these drips will be changed according to your blood glucose levels. Your blood glucose levels will be checked at least every hour.

Once born, your baby will be monitored closely, and may have blood tests regularly. This is to test for low sugar levels, not diabetes. They may need to go to the special care nursery for a day or two.

When baby is born

Once your baby is born your glucose and insulin drip will be stopped. You should be able to start eating fairly soon after delivery. Your blood glucose levels will be checked often. If they go up you will need either diabetes tablets or insulin.

Insulin is safest to take if you are breastfeeding. However, once you stop breastfeeding you can consider diabetes tablets again. Your baby's blood glucose will also be checked often in the first few days following birth. 

Once you go home it is important to stay in touch with the diabetes team until your blood glucose levels are healthy and you are settled on the medication you are taking for your diabetes.

Learn more

Pregnancy Diabetes New Zealand
Pre-Existing Diabetes and Pregnancy CDC, US Dept of Health 


  1. Monitoring diabetes before, during and after pregnancy BPAC, July 2015
  2. Diabetes in pregnancy: management from preconception to the postnatal period NICE, February 2015
Credits: Health Navigator team.