Diabetes and Pregnancy

Authored by , Reviewed by Dr Colin Tidy | Last edited | Meets Patient’s editorial guidelines

Sometimes pregnancy causes the blood sugar to go up in women who do not have diabetes. This is called gestational diabetes. Women who have diabetes also need extra care during pregnancy and should discuss this with a healthcare professional when they are considering starting their family.

Diabetes mellitus (just called diabetes from now on) occurs when the level of sugar (glucose) in the blood becomes higher than normal. There are two main types of diabetes. These are called type 1 diabetes and type 2 diabetes.

For further information about diabetes, see the separate leaflets called Type 1 Diabetes and Type 2 Diabetes.

Sometimes pregnancy causes the blood sugar to rise in women who do not have diabetes. This is called gestational diabetes (see below).

How does pregnancy affect diabetes?

Dr Partha Kar

Pregnancy makes the body need more insulin to control the levels of sugar (glucose) in the body. Therefore, women with diabetes usually need more treatments to control their blood sugar when they are pregnant.

If the diabetes is not well controlled during the pregnancy this may cause harm for both you and your baby. Therefore you will need more regular check-ups with a doctor, and to see a specialist during the pregnancy. This will help to reduce the risks and help you to stay well and have a healthy baby.

Gestational diabetes mellitus (GDM) is a term for diabetes which starts for the first time during pregnancy. It usually resolves soon after the woman gives birth. Research shows that GDM occurs in between 1 in 20 and 1 in 50 of all pregnancies. GDM usually starts in the second half of pregnancy.

The risks of having GDM for you and your baby are similar to those for mothers who have known diabetes, such as difficulties with giving birth and a higher chance of needing a caesarean section (see below). Most women with GDM recover after the pregnancy but there is a high risk of it returning (recurrence) in a future pregnancy. Women who have had GDM are also at increased risk of developing diabetes in the future.

Risk factors

GDM is more common for women at an older age when pregnant, women who are overweight (BMI above 30) and women who smoke. There is also an increased risk for:

  • Women who have had GDM in previous pregnancies.
  • Where there has been a short time interval between pregnancies.
  • Women who have had a previous unexplained stillbirth.
  • Women who have had a previous baby with very high birth weight (4.5 kg or more).
  • Women with an immediate family member (brother, sister or parent) with diabetes.
  • Some ethnic groups (South Asian, black Caribbean and Middle Eastern).


The glucose tolerance test (GTT) can be used to test for GDM. The current National Institute for Health and Care Excellence (NICE) guidance recommends that:

  • Woman who have had GDM in a previous pregnancy should be offered early self-monitoring of blood sugar (glucose) or a two-hour 75 g GTT as soon as possible after the first antenatal appointment. This is followed by a repeat GTT at 24-28 weeks of pregnancy if the first test is normal.
  • Women with other risk factors (see above) should have a GTT at 24-28 weeks.


GDM can cause serious consequences for you and your baby but these can be greatly reduced by treatment.

Treatment includes following advice about diet and physical activity. Medicines to lower your blood sugar levels may be required. The medicines may be tablets (for example, metformin) but insulin injections may also be needed.

After your pregnancy

Insulin and other medicines to control your blood sugar are usually stopped immediately after delivery.

Most women with GDM recover after the pregnancy but there is an increased (2 in 3) risk of it returning in a future pregnancy. Women who have had GDM are at increased risk of developing diabetes in the future. It is recommended that women with GDM:

  • Avoid being overweight.
  • Take regular exercise.
  • Don't smoke.
  • Try to avoid having pregnancies with only a short time (for example, a few months) between each pregnancy.
  • Attend the six-week postpartum check and have a blood sugar test taken.
  • Have their blood sugar level checked each year.

The risk of problems for you and your baby can be greatly reduced by the following advice:

  • Avoid unplanned pregnancies. It is very important to plan any pregnancy and so contraception is very important.
  • Good control of blood sugar (glucose) levels before and during pregnancy reduces the risks of stillbirth, miscarriage, congenital malformation and neonatal death.
  • It is essential to follow dietary advice, weight control and exercise advice given to all people with diabetes.
  • Make sure you are regularly checked for any complications of diabetes, including regular eye assessments and other assessments and appointments with your practice nurse, GP or specialist.
  • If you are planning to become pregnant then you should take 5 mg of folic acid daily until 12 weeks of pregnancy to reduce the risk of birth defects in your baby.
  • Ketone testing strips should be used to test for ketones if you become unwell. Ketones are substances the body makes if there is a lack of insulin in the blood.
  • If you smoke then it is even more important to stop smoking before pregnancy.
  • Reduce or cut down on the amount of alcohol you drink.
  • Think very positively about breastfeeding because it improves blood sugar control and makes it easier to lose weight after giving birth.

Editor's note

Dr Sarah Jarvis, January 2021

Glucose monitoring if you have diabetes in pregnancy 

NICE has updated its guidance on managing your diabetes if you are pregnant or planning to become pregnant.

It recommends that:

  • If you have type 1 diabetes, you should be offered continuous glucose monitoring (CGM). This can help you and your baby.
  • If you have type 1 diabetes but cannot use CGM, you should be offered intermittently scanned CGM (commonly referred to as flash glucose monitoring).
  • If you do not have type 1 diabetes but are pregnant and using insulin, your team should consider offering you CGM if:
    • You have problematic severe 'hypos'; or
    • Your blood glucose in unstable despite your best efforts.

There are various complications that may occur. Pre-conception care and good blood sugar (glucose) control before and during pregnancy can reduce these risks.

Problems during pregnancy

  • Premature birth: babies are more likely to be born early (before 37 weeks).
  • There is an increased risk of miscarriage or of the baby dying late in the pregnancy (stillborn).
  • Babies tend to be a higher birth weight and this may make giving birth much harder. There is an increased risk of your baby becoming distressed during labour (fetal distress).
  • There may be too much fluid around your baby (polyhydramnios).
  • You may experience more infections during the pregnancy and the infections may be severe.
  • There is an increased risk of needing to give birth by caesarean section.

Problems for the baby after pregnancy

Problems for the mother

  • There is an increased risk of problems during the pregnancy, including high blood pressure and blood clots.
  • There is an increased risk of the blood sugar being very high (ketoacidosis) or too low.
  • There is also risk that long-term diabetes complications may become worse, including eye problems and kidney problems.

You will need frequent checks during your pregnancy. It is essential to have regular checks of your diabetes control and checks of your baby. You will also need the checks that all women need during pregnancy. A specialist will be involved to help look after your diabetes and your unborn baby.

It is recommended that women who have diabetes give birth in hospital. There is a risk that your baby may be distressed and it is essential that specialised care is immediately available.

Although there is a risk of many problems for you and your baby, frequent checks and good treatment will help to make sure that you stay well and have a healthy baby.

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Further reading and references

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