May 14, 2019
Keio University School of Medicine
Project Professor Takeshi Miyamoto of the Endowed Department of Advanced Therapy for Orthopedic Disorders, Keio University School of Medicine (also a professor in the Department of Orthopedic Surgery, Graduate School of Life Sciences, Kumamoto University) and his colleagues have reported that primary low bone mineral density, not associated with metabolic or endocrinological diseases, is a suspected cause of vertebral fractures (compression fractures of the spine) that occur after childbirth.
In this study, an investigation of patients who experienced vertebral fractures after childbirth revealed that they showed a decrease in bone mineral density comparable to that seen in elderly patients with osteoporosis, despite not having metabolic or endocrinological diseases that are generally causes of osteoporosis. These patients had been exclusively breastfeeding until they sustained the fractures, and all of them fractured within three months of giving birth. To confirm the association with exclusive breastfeeding, an investigation of 79 women who visited the Department of Obstetrics and Gynecology at Keio University Hospital for childbirth showed that none of them had experienced vertebral fractures. Among them, the 34 women who were exclusively breastfeeding had significantly higher bone mineral density compared to the patients who had fractures, and their bone mineral density was comparable to that of women who were formula-feeding.
On the other hand, when the measurement results of bone turnover markers were compared between the two groups (exclusive breastfeeding and formula-feeding), the exclusive breastfeeding group showed that while the activity of bone formation was comparable to the other group, the activity of bone resorption was significantly higher, suggesting that lactation affects bone metabolism.
From the above results, it was concluded that it is extremely rare for pregnancy, childbirth, or lactation to cause low bone mineral density or fractures (0 out of 79 women), and that in the cases of vertebral fractures, the fractures occurred when postpartum exclusive breastfeeding caused changes in bone metabolism in women who already had remarkably low bone mineral density, with the addition of physical stress, such as holding an infant.
In recent years, with the advent of an aging society, awareness of osteoporosis in the elderly has increased. However, as awareness is low among younger people, this study is considered an important discovery that suggests the need for women considering pregnancy to undergo bone mineral density testing.
The results of this research were published on May 13, 2019 (UK time), in the online edition of the interdisciplinary general journal "Scientific Reports."
For the full press release, please see below.