In every pregnancy, a woman starts out with a 3-5% chance of having a baby with a birth defect. This is called her background risk. This sheet talks about whether exposure to bisphosphonates may increase the risk for birth defects over that background risk. This information should not take the place of medical care and advice from your health care provider.
What are bisphosphonates?
Bisphosphonates are a class of drugs that prevent the loss of bone mass. Risedronate (Actonel®), ibandronate (Boniva®) and alendronate (Fosamax®) are examples of bisphosphonates, but there are others. They are commonly used for the treatment of osteoporosis (higher fracture risks due to loss of bone density). They are also used in the treatment of Gaucher disease. For more information on Gaucher disease, see the MotherToBaby fact sheet at http://www.mothertobaby.org/files/Gaucher_disease.pdf. Bisphosphonates work to decrease the rate of bone remodeling (a normal process that replaces old bone with new bone deposits).
How long do bisphosphonates stay in the body? Should I stop taking them before I try to become pregnant?
Bisphosphonates leave a woman’s blood very quickly. However, 20-80% of the amount of the drug that enters the blood is then stored in bone tissue. Bisphosphonates can stay inactive in the bone tissue for years. They can also be released into the blood as the bone is remodeled. Stored bisphosphonates might be released from bones during pregnancy.
Based on theoretical concerns about the effects on fetal bones, treatment with bisphosphonates is usually stopped before conception. However, in three women with severe bone disease, bisphosphonates were used prior to and in early pregnancy, with some evidence that normal pregnancy bone loss was lessened.
I have been taking bisposphonates and just found out I am pregnant. Should I stop?
No. You should not stop taking any medication without first talking to your health care provider. The benefits of treatment need to be evaluated against any possible risk to a pregnancy.
Can taking bisphosphonates during pregnancy cause a birth defect?
Concern has been raised about the use of bisphosphonates in animal pregnancies. Studies found that rats given bisphosphonates during pregnancy developed calcium deficiency (hypocalcemia), which led to abnormal bone development, and also slow, difficult labor and delivery. Effects related to low calcium are not expected in women on bisphosphonates, as they typically do not cause low calcium levels in people.
Small studies and case reports that included around 70 women using bisphosphonates prior to or during pregnancy have not shown an increase in the rate of birth defects or long term health concerns. In addition, several small studies of the use of bisophosphonates in infants and young children have shown normal bone development. There are no well-designed studies of bisphosphonate use during pregnancy.
Can taking bisphosphonates during pregnancy cause other pregnancy complications?
Miscarriage and low birth weight have been reported in women with Gaucher disease treated with bisphosphonates in pregnancy. However, it is not known whether these complications were due to the bisphosphonate treatment, other medication(s)/treatment(s) for Gaucher disease, or the disease itself.
Is it safe for me to take bisphosphonates while I am breastfeeding?
Bisphosphonates are generally not recommended during breastfeeding because they are stored in bone tissue, and have the theoretical potential to affect the infant’s bone development.
There are no studies looking at bisphosphonates and breastfeeding. They are expected to pass into breast milk. Bisphosphonates are very poorly absorbed when taken by mother, and the amount a nursing infant might absorb is likely very small. There is a single case report of a nursing mother treated with bisphosphonates. Small amounts of bisphosphonate were found in her milk, but no harmful effects were seen in the baby. Be sure to talk to your health care provider about all your choices for breastfeeding.
Is there a concern if my partner was taking bisphosphonates when I got pregnant?
There are no studies looking at paternal use of bisphosphonates prior to or at the time of conception. In general, exposures that fathers have are unlikely to increase risks to a pregnancy. For more information, please see the MotherToBaby fact sheet Paternal Exposures and Pregnancy at http://www.mothertobaby.org/files/paternal.pdf.
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