Selective serotonin reuptake inhibitors (SSRIs) use during pregnancy and lactation can result in decreased bone density in mothers, increasing their risk of fractures later in life, a study presented at ENDO 2016 has found.

Previous data has found that SSRI use can lower bone mineral density and increase the fracture risk in both adolescents and adults. Women who do not take SSRIs typically lose 6–10% of their bone mass while nursing due to calcium being redirected from bones to breast milk. Though most women recover bone loss within a year of discontinuing breastfeeding, new evidence has shown women who breastfeed for longer periods have a higher risk of low bone density post-menopause.

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Laura Hernandez, PhD, principal study investigator, and colleagues set out to examine whether SSRIs have an additive effect on bone loss during lactation. They administered fluoxetine (Prozac) to 6 mice during pregnancy and lactation along with their regular diet and compared them to 6 female mice that received saline. Two other groups of mice were fed a diet supplemented with high folic acid prior to breeding and then were administered fluoxetine or saline during pregnancy and lactation.

On Day 10 of lactation, study authors analyzed bone mineral density in the mice’s femur and tested gene expression in the animals’ mammary glands. Both mice groups that received fluoxetine had higher serotonin reuptake by the mammary gland, which seemed to stimulate bone resorption. The fluoxetine groups expressed lower amounts of osteocalcin at the femur vs. groups that were given saline. In addition, the fluoxetine groups showed higher levels of macrophage colony-stimulating factor in the femur, which is responsible for bone resorption.

The high dose of folic acid appeared to reverse the SSRI effects on the bone, study authors reported. Dr. Hernandez pointed out that women who breastfeed may require more folic acid to protect against bone loss.

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