According to a study published in the journal PLOS ONE, reproduction permanently changes the bone structure of females. The researchers claimed that the skeleton is not a static organ but a dynamic one that changes with life events.

The study revealed that calcium, magnesium, and phosphorus concentrations were found to be lower in females who have experienced reproduction in comparison to males as well as females who did not give birth.

As per the findings, calcium and phosphorus were found to be at lower concentrations in the bone formed during reproductive events, while a significant decline in magnesium concentration was observed during the breastfeeding period of the infants. 

(Source: https://theprint.in/health/study-reveals-how-female-bones-permanently-change-after-giving-birth/1192028/ )