Bone mineral density in grand multiparous women with extended lactation

OBJECTIVE: We sought to assess whether the accumulation of multiple, frequent pregnancies and the accompanying repeated extended lactation events was a risk factor for low bone mineral density and osteoporosis. STUDY DESIGN: The study population consisted of 30 grand multiparous women who had borne at least 6 children and lactated for at least 6 months with each child, as well as 6 nulliparous, premenopausal women from a population of Finnish American women associated with the Laestadian Church in Washington State. The Church membership has not embraced contraception or extensive bottle-feeding, resulting in a group of women who are either pregnant or lactating during most of their adult reproductive lives. The medical history included the delivery date, birth outcome, infant birth weight, and number of months lactated for each pregnancy, as well as other health information. Bone mineral density of the lumbar spine, femoral neck, and radius was measured with the Hologic QDR 4500-C dual-energy x-ray absorptiometry scanner. Proc Genmod, SAS version 6.14 (Statistical Analysis Systems, Inc, Cary, NC), was used to perform a Wilcoxon test for a nonparametric analysis of covariance and significance adjusted for age and body size. RESULTS: The 2 study groups did not differ in terms of body mass index, history of smoking, or family history of osteoporosis and fracture, although the parous group was, on average, 8 years older than the nulliparous group (P < .05). The accumulation of repeated pregnancy and lactation events without a recovery interval was not associated with lowered bone mineral density or the presence of osteoporosis or osteopenia. CONCLUSIONS: This study suggests that bone mineral density levels can be sustained in the presence of the rapidly changing hormone environment associated with multiple pregnancies accompanying lactation events without a "recovery" interval.