Forearm bone mineral density changes during postpartum and the effects of breastfeeding, amenorrhea, body mass index and contraceptive use

Prospective cohort study performed to evaluate bone mineral density (BMD) changes up to 12 months postpartum of healthy women and its association with breastfeeding, contraceptive methods, amenorrhea, and body mass index (BMI). There is a trend in bone loss during the first 6 months with posterior recovery, with evidence of a protective effect of hormonal contraception. This study was conducted to evaluate bone mineral density (BMD) changes during postpartum period among healthy women and its association with breastfeeding, use of contraceptive methods, amenorrhea and body mass index (BMI). A prospective cohort study including 100 healthy women. Distal BMD was measured 7-10 days, 3, 6, and 12 months postpartum at the nondominant forearm using dual-energy X-ray absorptiometry. Data about breastfeeding duration, amenorrhea, contraceptive use and BMI were collected. Seventy-eight women had a complete set of BMD measurements. The mean duration of exclusive breastfeeding was 125.9 (+/- 66.6) days, with a median total lactation period of 263.5 days. The mean duration of amenorrhea was 164.2 (+/- 119.2) days. BMD measurements showed a significant decrease in the distal radius, however with no significance in the ultradistal radius. When considering only the nonhormonal contraceptive users, the difference at 12 months was significant. Multivariate analysis of variance showed that both BMI and contraceptive use were significantly correlated with BMD. Multiple linear regression analysis showed significant correlation of distal radius with baseline BMD at the same site, pregestational BMI, age, years of schooling and difference in BMI. For ultradistal radius, there was a significant direct correlation with its baseline BMD and pregestational BMI. There was a trend in bone loss during the first 6 months postpartum with posterior recovery. Also, hormonal contraceptive methods provided protection of bone loss. However, the long duration of breastfeeding and the follow-up were not sufficient to draw definitive conclusions on postweaning BMD conditions.