How Does Pregnancy or Breastfeeding Affect the Risk of Osteoporosis?
During pregnancy, the developing fetus accumulates about 30 grams of calcium to build its own skeleton. That’s 30,000 mg of calcium that must be transferred from the mother’s body to the fetus. During breastfeeding, another 300 to 400 milligrams of calcium are removed from the mother’s body daily in the form of breast milk. In fact, a woman breastfeeding twins can lose as much as 1,000 milligrams of calcium daily through milk production.A Woman’s Body Can Conserve Calcium
With such substantial demands on calcium during pregnancy and breastfeeding, researchers have investigated how having children might affect a woman’s risk of osteoporosis later in life. Fortunately, when a woman is pregnant, her body becomes more efficient at absorbing calcium from foods and her kidneys adapt by decreasing calcium losses in the urine. Even with these adjustments, there is typically some bone loss during the last months of pregnancy.During breastfeeding, additional bone loss occurs, even with a high calcium intake. After weaning, bones can increase their uptake of calcium and rapidly restore calcium back to pre-pregnant levels if adequate calcium is present in the diet.
In the vast majority of normal healthy women, pregnancy and breastfeeding a baby results in a temporary loss of calcium from bones that is rapidly replenished after breastfeeding is finished.
Consequently, there is typically no effect on the long-term risk of osteoporosis.
Some Rare Problems
Although it is uncommon, some women have experienced low bone density and bone fractures during or shortly after pregnancy or during breastfeeding. Little is known about the causes of these rare occurrences, but they may be related to a woman having low bone density at the start of pregnancy. If bone density is too low, her bones may be unable to tolerate the normal temporary losses of calcium that occur. Researchers also think that unusual hormone fluctuations can be involved in some cases.An old adage says that a woman should expect to lose a tooth for every child she has. If calcium intake is limited, there may be a touch of truth to this. A study published in the January 2007 issue of the Journal of Periodontology reported that female rats were more likely to lose supportive bone around the teeth when they were nursing their young and consuming a lower calcium diet. It makes sense to take a hint from the rats and keep up the calcium in your diet during breastfeeding.
Pregnant Teens
A pregnant teenager has high calcium needs for her own skeletal development. Consequently, there is some concern that the demands of fetal development could compromise the accumulation of peak bone mass for the teen mother. This concern is controversial, but provides extra reasons to encourage overall good nutrition and adequate calcium intake.The Bottom Line
Bone density and fracture incidence are about the same in women who have had many children and those who have never been pregnant. A woman’s bones are well designed to deal with the demands of pregnancy as long as her diet provides an adequate supply of all nutrients.
Sources
Bone Health and Osteoporosis: A Report of the Surgeon General. (2004), U.S. Department of Health and Human Services, Public Health Service, Office of the Surgeon General. (Report)
Kovacs, Christopher S. “Calcium and Bone Metabolism During Pregnancy and Lactation.” Journal of Mammary Gland Biology and Neoplasia 10 (2005): 105-18.
(Article Abstract)
Shoji, Kanako, et al. “Effects of Lactation on Alveolar Bone Loss in Experimental Periodontitis.” Journal of Periodontology (2007): 152-56. (Article Abstract)