Long term effects of reproductive history on bone mineral content in women.

Bone loss among the elderly is of increasing concern to the medical community. In a study combining retrospective data on 438 women from southern Arizona and current bone mineral values determined at the one-third distal radius, the effects of premenopausal reproductive events on postmenopausal bone mineral are investigated. Among those women who reach menarche at an early age are some whose growth is not accompanied by normal height and long bone growth. These women tend to exhibit lower bone mineral density postmenopausally. In addition, the early accumulation of weight in excess of height and a later age at menarche appears to result in wider bones still observed postmenopausally. Pregnancy normally is accompanied by an acceleration of calcium accumulation in excess of the fetal demand. However, parity appears to have little significant impact on postmenopausal bone mineral status. However, women pregnant during their teens tend to accumulate a greater amount of bone than women who first become pregnant later. These benefits to the teenage mother can be lost during lactation, an impairment of the skeleton which may continue into the postmenopausal years. The skeleton appears to require a recovery period between pregnancy and lactation cycles. Inadequate recovery time, particularly when accompanied by advanced maternal age, may have adverse effects on postmenopausal bone mineral status