Metal-on-metal hip joints

Date: October 2022, Version 3

Quick read

Metal-on-metal (MOM) hip joints are unlikely to affect a pregnancy. Women with an MOM hip who are planning a pregnancy should speak to their doctor.

What are they?

Metal-on-metal (MOM) artificial hip joints (also called MOM hip implants) are made of cobalt or chromium. MOM implants are rarely used because they wear out more quickly than other types of hip joint.

Are there any concerns about a metal-on-metal hip joint affecting a pregnancy?

People with an MOM hip joint sometimes have increased blood levels of cobalt or chromium, particularly in the first few months after surgery, or if the hip is wearing out.

Increased blood metal levels do not usually cause ill health, but it is unclear whether they might affect a developing baby during pregnancy.

The available information does not suggest that pregnant women with MOM hip joints are at increased risk of having a baby with a birth defect, or other pregnancy problems. However, there is only a small amount of available information as MOM hip joints are rare in women of childbearing age. Because the majority of people with MOM joints have normal blood metal levels, there is no information on pregnancy outcomes specifically in women with high levels of cobalt or chromium.

What if I have a metal-on-metal hip joint and want to get pregnant?

Women with an MOM hip joint who are planning a pregnancy should speak to their GP. The doctor will assess the risk of high metal levels by considering how long the hip joint has been in place and asking about symptoms that could suggest the joint is wearing out. They will check when blood metal levels were last measured and may arrange blood tests. Women may also be referred to a specialist doctor for further monitoring.

Many women will be advised that their hip joint is unlikely to affect a pregnancy.

If high blood metal levels are detected and the joint was implanted recently, a doctor may advise that, where possible, conception is delayed for up to two years after the hip replacement to allow the metal levels to naturally settle. Repeat blood tests might be offered during this period.

If metal levels are high because a hip joint is failing, a specialist might advise further tests and possibly surgery to implant a different type of hip joint. Metal levels will drop once the MOM hip is removed.

In practice, some women may not want to delay pregnancy while waiting for high blood metal levels to drop. The doctor or specialist will be help with weighing up the benefits and possible risks of delaying conception compared to attempting to conceive sooner.

If I become pregnant with a metal-on-metal hip joint, will my baby need extra monitoring during pregnancy?

As part of their routine antenatal care, most women in the UK will be offered a detailed scan at around 20 weeks of pregnancy to look for birth defects and to check the baby’s growth.

The majority of women with an MOM hip joint in place during pregnancy will not require any extra scans. However, additional checks of the baby might be offered to pregnant women with high blood metal levels.

Are there any risks to my baby if the father has a metal-on-metal hip?

There is no evidence that metal from an MOM hip joint can affect the sperm and therefore cause problems in the baby.

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 healthcare provider. They can access more detailed medical and scientific information from www.uktis.org.

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.