主题：【原创】送给孝子：骨质疏松 -- 虽远必诛

a prospective study of bone mineral density (BMD) in 38 women during their first full-term pregnancy until 12 months postpartum. BMD measurements at lumbar spine [L2–L4 (LS)] and forearm [distal 33% (RD) and ultradistal (RUD) region of the radius] were made within 3 months before conception, after delivery, and at 6 and 12 months postpartum. In mid-pregnancy the DXA examination was carried out only at the forearm. Patients were grouped according to duration of lactation as group I, II or III (0–1, 1–6, 6–12 months respectively). During pregnancy there was a significant difference between baseline and delivery (p< 0.001) in the LS, RUD and RD BMD values. In group I there was no statistically significant difference in LS BMD between visits following pregnancy. The RUD BMD loss was recovered by 6 months postpartum (PP6). Group II showed continuous bone loss from delivery until PP6 at LS and RUD. In group III the LS BMD loss continued throughout the lactation period. The RUD BMD dropped (4.9%) until PP6 then increased by 3.0% as measured at 12 months postpartum (PP12). There was no significant change in RD BMD in any of three groups during lactation. At LS bone loss between delivery and PP12 correlated well with the duration of lactation (r=0.727; p<0.001). We suggest that calcium needed for fetal skeletal growth during pregnancy was gained from maternal trabecular and cortical sites and that calcium needed for infant growth during lactation was drawn mainly from the maternal trabecular skeleton in our patients. The effect of pregnancy and lactation on the maternal bone mass was spontaneously compensated after weaning.

Women who had "late fertility" - a birth at age 45 or older - were 14 percent to 17 percent less likely to die during any year after age 50 than women who did not deliver a child after age 40. That confirmed earlier studies. But those studies did not determine if the women gave birth later and lived longer because of genes or because of social and environmental factors such as good nutrition or healthy living.

Brothers who had at least three sisters, including at least one sister who gave birth at age 45 or later, were 20 percent to 22 percent less likely to die during any year after age 50 than brothers who had no "late fertile" sisters. That indicates what earlier studies did not, namely, the same genes may influence the lifespan of both sexes and women's ability to give birth at older ages.

"The baby boomers of today are doing the right thing by having children much later - because the evidence is that the later you produce children, the longer your life span will be," said Dr Dawn Skelton of Manchester University, a leading authority on ageing.

She tells a television documentary to be shown next month: "After 30, there is a dramatic reduction of the oestrogen hormone in women. By leaving it longer before having our first child, we're giving ourselves a big burst of oestrogen, which helps in many ways - muscle, bone, nervous function."

Later motherhood holds benefits as well as drawbacks. Older women find it more tiring but it also seems to bring longevity.

In their studies of centenarians, Perls and Fretts found that a surprising number of women who lived to be 100 or more gave birth in their forties. These 100-year-old women were four times as likely to have given birth in their forties as women born in the same year who died at age 73. A study of centenarians in Europe by the Max Planck Institute of Demography in Germany found the same relationship between longevity and fecundity.

Many centenarian women have a history of bearing children after the age of 35 years and even 40 years. From our studies, a woman who naturally has a child after the age of 40 has a 4 times greater chance of living to 100 compared to women who do not (6). It is probably not the act of bearing a child in one’s forties that promotes long life, but rather, doing so may be an indicator that the woman’s reproductive system is aging slowly and that the rest of her body is as well. Such slow aging and the avoidance or delay of diseases that adversely impact reproduction would bode well for the woman’s subsequent ability to achieve very old age.