Pregnancy is a true hormonal revolution for women, who experience numerous changes in the body throughout pregnancy, but, in addition, a new study has confirmed that the reproductive process permanently alters the bones of the mothers – to be more specifically, of the primate females in which the study has been carried out–, in a way unknown until now and that reveals new clues about how giving birth can permanently change the body.
A team of anthropologists has discovered that the bone composition of the primate females analyzed showed irreversible changes after giving birth and nursing their young. “Our findings provide additional evidence of the profound impact that reproduction has on the female organism, further demonstrating that the skeleton is not a static organ, but a dynamic one, which changes with life events,” explains Paola Cerrito, who has led research and is a doctoral student in the New York University Department of Anthropology and School of Dentistry.
Specifically, the researchers found that the concentrations of calcium, magnesium and phosphorus are lower in females that have reproduced and that these changes are related to childbirth and lactation. They have also cautioned that while other clinical studies show that calcium and phosphorous are key to maintaining strong bones, their findings do not address general health implications for either primates or humans, but instead open a pathway for knowledge about the dynamic nature of our bones.
“These findings reaffirm the significant impact that giving birth has on a female body; simply, the evidence of reproduction is ‘written in the bones’ for life”
“A bone is not a static, dead part of the skeleton,” says New York University anthropologist Shara Bailey, one of the study’s authors. “It continually adjusts and responds to physiological processes.” The results of the work have been published in PLOS ONE.
How reproduction affects the composition of the skeleton
Menopause can have a significant impact on female bones, but it was unclear how other events earlier in the life cycle, such as reproduction, influenced skeletal composition. To try to find out, the researchers analyzed the primary lamellar bone, which is the main type of bone in a mature skeleton and is an ideal part to study why it changes over time and leaves biological markers of these changes that allow monitoring alterations to throughout life.
The scientists examined the growth rate of lamellar bone in the femur, or thigh bones, of male and female primates that had lived at the Sabana Seca Field Station in Puerto Rico and had died of natural causes. Veterinarians at the field station had monitored and recorded data on the health and reproductive history of these animals, which allowed the researchers to link changes in bone composition to life events very precisely.
Cerrito and his colleagues used electron microscopy and energy dispersive X-ray analysis, techniques commonly used to measure the chemical composition of tissue samples and calculate changes in the concentrations of calcium, phosphorus, oxygen, magnesium, and sodium in primate bones.
Females that gave birth had different concentrations of some of these elements compared to males and females that did not give birth. Calcium and phosphorus were lower in the bones formed during reproductive events in the females that gave birth, and there was also a significant reduction in magnesium concentration during lactation in these primates.
“Our research shows that even before the cessation of fertility, the skeleton responds dynamically to changes in reproductive status,” explains Cerrito, now a researcher at ETH Zurich. “Furthermore, these findings reaffirm the significant impact that giving birth has on a female body; simply, the evidence of reproduction is ‘written in the bones’ for life”.
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