Metal-on-metal (MoM) hip joints

Quick read

Most pregnant women with a metal-on-metal (MoM) hip joint will not experience complications. If your hip joint is causing high blood metal levels, extra monitoring of your baby might be offered.

What are they?

Metal-on-metal hip joints (also called metal-on-metal hip implants) are artificial hip replacements made of cobalt or chromium. Metal-on-metal implants are now rarely used because they can wear out, cause unpleasant symptoms, and release metals into the bloodstream. All people with a metal-on-metal hip should receive regular monitoring to check for signs of the implant wearing out.

Because metal-on-metal hip implants used to be widely used, some women of childbearing age may have one in place.

Are there any risks of a metal-on-metal hip joint affecting a pregnancy?

People with a metal-on-metal hip joint sometimes have higher levels of cobalt or chromium in their blood, particularly 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 small amount of available information does not suggest that pregnant women with metal-on-metal hip joints are more likely to have a baby with a birth defect, or other pregnancy problems. However, there is very little information about pregnancy outcomes specifically in women whose metal-on-metal hip has caused high blood levels of cobalt or chromium, so we do not know if this could be harmful. 

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

If you have a metal-on-metal hip joint and are planning a pregnancy, speak to your GP for advice. You may be referred to a specialist doctor (an orthopaedic surgeon). They will ask you about any symptoms that could suggest your hip joint is wearing out and might offer blood tests to check metal levels.

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

If metal levels are high because a hip joint is failing, a specialist might advise surgery to replace it with a different type of hip joint. Metal levels will fall once the metal-on-metal hip joint is removed. 

In some cases, women may not want to delay pregnancy. Your specialist will help you to weigh up the benefits and possible risks of delaying pregnancy 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?

Women in the UK are routinely 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 a metal-on-metal 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 a metal-on-metal hip joint can affect 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.