Date: April 2022, Version 3

What is it?

Metformin is mainly used to treat type 2 diabetes and gestational diabetes.


What are the benefits of using metformin in pregnancy?

Metformin helps to control blood sugar levels in people with diabetes. Good blood sugar control is essential to reduce the likelihood of ill-effects caused by diabetes including damage to the blood vessels, nerves, and eyes.

Poorly controlled type 2 diabetes in pregnancy increases the chance of miscarriage, birth defects in the baby, stillbirth, and death of the baby just after delivery.

Poorly controlled gestational diabetes is linked to having a bigger baby, delivery complications and problems with the baby’s blood sugar levels after birth.


What are the risks of using metformin during pregnancy?

There are no known risks of using metformin in pregnancy.


Are there any alternatives to using metformin in pregnancy

Not usually — metformin is generally the first-choice drug for treatment of diabetes in pregnancy.

Women who are taking metformin before pregnancy will likely be advised to continue, as this tends to be safest for both mother and baby.

Some women may also need to use insulin alongside metformin to ensure good blood sugar control.

Women using metformin who are planning a pregnancy or become pregnant should let their doctor know — they will assess whether it needs to be continued and ensure the dose is correct.

No treatment

What if I prefer not to use metformin in pregnancy?

It is very important that blood sugar levels are well-controlled in pregnancy to avoid adverse effects for both mother and baby. Using metformin is often the safest way to ensure this.

Are there any risks to my baby if the father uses metformin?

A study published in 2022 found a possible link between use of metformin by the father around the time of conception and genital malformations in male babies. However, diabetes itself is known to affect sperm quality and further research is required to find out if the effects seen in male babies are caused by metformin or by diabetes/poor blood sugar control in the father.

Will I or my baby need extra monitoring during pregnancy?

Use of metformin during pregnancy is not expected to cause any problems that would require extra monitoring of the baby.

Pregnant women with diabetes are more likely to have a larger than average baby — extra monitoring of their baby’s growth will therefore be offered.

Who can I talk to if I have questions?

If you have any questions regarding the information in this leaflet, please discuss them with your health care provider. They can access more detailed medical and scientific information from

How can I help to improve drug safety information for pregnant women in the future?

Our online reporting system (MyBump Portal) allows women who are currently pregnant to create a secure record of their pregnancy, collected through a series of questionnaires. You will be asked to enter information about your health, whether or not you take any medicines, your pregnancy outcome and your child's development. You can update your details at any time during pregnancy or afterwards. This information will help us better understand how medicines affect the health of pregnant women and their babies. Please visit the MyBump Portal to register.

General information
Sadly, miscarriage and birth defects can occur in any pregnancy.

Miscarriage occurs in about 1 in every 5 pregnancies, and 1 in every 40 babies are born with a birth defect. This is called the ‘background risk’ and happens whether medication is taken or not.

Most medicines cross the placenta and reach the baby. For many medications this is not a problem. However, some medicines can affect a baby’s growth and development.

If you take regular medication and are planning to conceive, you should discuss whether your medicine is safe to continue with your doctor/health care team before becoming pregnant. If you have an unplanned pregnancy while taking a medicine, you should tell your doctor as soon as possible.

If a new medicine is suggested for you during pregnancy, please make sure that the person prescribing it knows that you are pregnant. If you have any concerns about a medicine, you can check with your doctor, midwife or pharmacist.

Our Bumps information leaflets provide information about the effects of medicines in pregnancy so that you can decide, together with your healthcare provider, what is best for you and your baby.