The relationship between parity, mode of delivery, age at childbirth and bone mineral density: a cross-sectional study

Abstract

Background As a neuro-psycho-social event, birth can impact the maternal health. The relationship between birth and bone health remains unclear, requiring further research to explore their association. Methods Our study was based on data from the National Health and Nutrition Examination Survey (NHANES) (2005-2020). Propensity score matching, Welch's two-sample t-test, Linear mixed models and Partial correlation analysis were used to examine the relationship between birth and BMD. Results We obtained 5727 participants. Welch's two-sample t-test showed that delivered subjects had lower mean BMD of the lumbar spine and lower limbs. The data from the linear mixed model showed a decrease in BMD of lower limbs and a decrease in BMD of lower spine in delivered subjects compared to those who had not. The same analyses showed lower BMD. Partial correlation analysis showed a negative correlation between age at birth and BMD in women who gave birth vaginally. Conclusions Women who have given birth have lower BMD compared to women who have not given birth. At the same time, BMD is negatively correlated with parity and age at delivery. Most importantly, we found for the first time a damaging association between vaginal delivery and BMD of lower limbs.