SAN DIEGO — The combination of breastfeeding and delaying pregnancy until the majority of bone mass has been acquired appears to have a protective effect on bones, according to study involving more than 600 women.
“Several studies have shown that people who have had many pregnancies have less bone loss than women with no pregnancies,” lead author Dr. Peter F. Schnatz said in an interview.
“Our study is the first to our knowledge looking at the effect of pregnancy during the time of peak bone mineral acquisition and its eventual and ultimate effect on the development of postmenopausal osteoporosis,” he said at a poster session at the annual meeting of the North American Menopause Society.
Dr. Schnatz, of the department of obstetrics and gynecology at Reading (Pa.) Hospital and Medical Center, and his associates analyzed data from 619 women aged older than 49 years who presented for bone density scanning in the Hartford, Conn., area. They assessed risk factors for osteoporosis, including a previous atraumatic fracture of the hip or spine, pregnancy information, and dual-energy x-ray absorptiometry results. Mean age of the study participants was 62 years; 50% were either current or past smokers.
Women who had breastfed had a significantly lower prevalence of osteoporosis (8%) than did those who did not breastfeed (19%), a finding that surprised the researchers. “It would seem that breastfeeding, which requires acquisition of calcium from the mother to nourish the baby, would cause bone loss,” Dr. Schnatz said. “We wonder if there may be a rebound anabolic phenomenon, hence resulting in overall benefit.”
Among those who had breastfed, women aged younger than 27 years at the first pregnancy had a significantly higher prevalence of osteoporosis than did those who were 27 and older at first pregnancy (11% vs. 5%, respectively).
Of those who were at least 27 years old at first pregnancy, there was a significantly increased prevalence of osteoporosis in those who did not breastfeed, compared with those who did (25% vs. 5%, respectively).
Women who were at least 27 years old at their first pregnancy and who breastfed had a statistically lower prevalence of osteoporosis, compared with their counterparts who had their first pregnancy younger than age 27 and no history of breastfeeding (5% vs. 16%, respectively).
Among women who did not breastfeed, there was little difference in the risk of postmenopausal osteoporosis if the first pregnancy occurred at or after age 22 or 27 years, Dr. Schnatz wrote.
“Women should be encouraged to wait until the postadolescent years for childbearing and should be encouraged to breastfeed,” he concluded.
The study was supported by a grant from the Alliance for Better Bone Health. Dr. Schnatz and his associates had no other financial conflicts to disclose.