Bisphosphonates

(Date: September 2017. Version: 3)

This factsheet has been written for members of the public by the UK Teratology Information Service (UKTIS). UKTIS is a not-for-profit organisation funded by Public Health England on behalf of UK Health Departments. UKTIS has been providing scientific information to health care providers since 1983 on the effects that medicines, recreational drugs and chemicals may have on the developing baby during pregnancy.

What are they?

Bisphosphonates (alendronic acid, ibandronic acid, pamidronate disodium, risedronate sodium, sodium clodronate and zoledronic acid) are medicines that are used to prevent bone degeneration. They are used to treat osteoporosis, bone loss caused by corticosteroid therapy, and in the treatment of conditions that affect the structure of bone such as Paget’s disease and osteogenesis imperfecta (brittle bone disease”), and bone pain caused by the spread of breast cancer. The bisphosphonates used in the UK are alendronic acid, ibandronic acid, pamidronate disodium, risedronate sodium, sodium clodronate and zoledronic acid.

Is it safe to use bisphosphonates in pregnancy?

At present, there is information on only 61 babies of women who were treated with bisphosphonates during pregnancy (see below). Although there is currently no suggestion that bisphosphonates cause birth defects or other serious problems, not enough pregnancies have been studied to be able to say whether or not use in pregnancy is safe. When deciding whether treatment with bisphosphonates in pregnancy is safe, it is therefore necessary for women and their doctors to weigh up the risks and benefits to both mother and baby of not taking a specific treatment against those of continuing the treatment. The outcome of this assessment will vary from person to person and will depend on the severity of the mother’s condition and the complications that could arise if her treatment is altered.

A summary of the studies providing information on the possible risks to a baby in the womb are summarised below. Some of these risks will depend on how many weeks pregnant you are.

What if I have already used a bisphosphonate during pregnancy?

If you are taking any medicines it is always a good idea to let your doctor know that you are pregnant so that you can decide together whether you still need the medicines that you are on or whether you might need to switch to a different medicine.

Can using a bisphosphonate in early pregnancy cause my baby to be born with birth defects?

A baby’s body and most internal organs are formed during the first 12 weeks of pregnancy. It is mainly during this time that some medicines are known to cause birth defects.

Neither of two small studies which together include a total of 45 babies exposed in early pregnancy to bisphosphonates found a link with birth defects in the baby. However, many more pregnant women taking bisphosphonates need to be studied to confirm this finding. 

Can using a bisphosphonate in pregnancy cause miscarriage?

Two small studies which together include a total of 45 babies exposed in early pregnancy to bisphosphonates have investigated the chance of miscarriage. While one study found that women taking bisphosphonates had a higher chance of miscarriage the other study did not. Furthermore, neither study considered the possible effects of underlying illnesses in the mothers in their analyses. No conclusions about bisphosphonate use in pregnancy and miscarriage risk can therefore be drawn. Further well-designed studies of many more women using bisphosphonates in pregnancy are therefore required to answer this question.

Can using a bisphosphonate in pregnancy cause stillbirth?

There were no stillbirths among a total of 61 pregnancies exposed to bisphosphonates that have been detailed in the scientific literature. Although this is reassuring, large studies that are designed to assess the chance of stillbirth following bisphosphonate exposure are required.

Can using a bisphosphonate in pregnancy cause preterm birth, or my baby to be small at birth (low birth weight)?

Two small studies which together include a total of 45 babies exposed in early pregnancy to bisphosphonates produced different findings with respect to the chance of preterm birth and low birth weight. One study found that babies exposed in the womb to bisphosphonates had a higher chance of preterm delivery or low birth weight than babies not exposed to bisphosphonates, while the other did not. However neither study accounted for the possible effects of underlying illnesses in the mothers, and how these results relate to bisphosphonate use rather than other factors is therefore unclear. Further well-designed studies of many more women using bisphosphonates in pregnancy are required to answer these questions.

Can using a bisphosphonate in pregnancy cause learning and behavioural problems in the child?

A baby’s brain continues to develop right up until the end of pregnancy. It is therefore possible that taking certain medicines at any stage of pregnancy could have a lasting effect on a child’s learning or behaviour.

No studies designed to scientifically investigate whether bisphosphonate exposure in the womb might affect a child’s learning and behaviour have been published. Individual case studies of nine children who had been exposed in the womb to bisphosphonates did not describe any problems with their learning and behaviour. All of these children were five years of age or younger when the reports were written. Problems with learning may not always be picked up until children are older. Further well-designed large studies of learning and behaviour in children exposed to bisphosphonates in pregnancy are therefore required to answer this question.

Will I or my baby need extra monitoring during pregnancy?

Most women will be offered a scan at around 20 weeks of pregnancy to look for birth defects as part of their routine antenatal care.

Because the effects of taking bisphosphonates in early pregnancy are largely unknown your doctor may suggest extra monitoring of your baby, including more detailed or earlier scans to detect birth defects, and more frequent review of your baby’s growth in the womb. Women with some of the conditions that bisphosphonates are used to treat may be more closely monitored anyway to ensure that their baby is growing and developing as expected.

There have been a small number of reports of babies exposed in the womb to bisphosphonates having abnormally low calcium levels in their blood at birth. If you have used bisphosphonates during pregnancy your baby’s blood calcium level may therefore be checked after delivery.

Are there any risks to my baby if the father has used a bisphosphonate?

There are no scientific reports of babies born to men who used a bisphosphonate around the time of conception. Most experts agree that the majority of medicines used by the father are unlikely to harm the baby through effects on the sperm. However, more research on the effects of bisphosphonates specifically and medicine use in men around the time of conception generally is needed.

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 www.uktis.org.

General information 

Up to 1 out of every 5 pregnancies ends in a miscarriage, and 1 in 40 babies are born with a birth defect. These are referred to as the background population risks.  They describe the chance of these events happening for any pregnancy before taking factors such as the mother’s health during pregnancy, her lifestyle, medicines she takes and the genetic make up of her and the baby’s father into account.

Medicines use in pregnancy

Most medicines used by the mother will cross the placenta and reach the baby. Sometimes this may have beneficial effects for the baby.  There are, however, some medicines that can harm a baby’s normal development.  How a medicine affects a baby may depend on the stage of pregnancy when the medicine is taken. If you are on regular medication you should discuss these effects with your doctor/health care team before becoming pregnant.

If a new medicine is suggested for you during pregnancy, please ensure the doctor or health care professional treating you is aware of your pregnancy.

When deciding whether or not to use a medicine in pregnancy you need to weigh up how the medicine might improve your and/or your unborn baby’s health against any possible problems that the drug may cause. Our bumps leaflets are written to provide you with a summary of what is known about use of a specific medicine in pregnancy so that you can decide together with your health care provider what is best for you and your baby.   

Every pregnancy is unique. The decision to start, stop, continue or change a prescribed medicine before or during pregnancy should be made in consultation with your health care provider. It is very helpful if you can record all your medication taken in pregnancy in your hand held maternity records.

   

www.medicinesinpregnancy.org

Disclaimer: This information is not intended to replace the individual care and advice of your health care provider. New information is continually becoming available. Whilst every effort will be made to ensure that this information is accurate and up to date at the time of publication, we cannot cover every eventuality and the information providers cannot be held responsible for any adverse outcomes following decisions made on the basis of this information. We strongly advise that printouts should NOT be kept for any length of time, or for “future reference” as they can rapidly become out of date.

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