An old adage says that for every child a woman has, she should expect to lose a tooth. When tooth loss occurs due to pregnancy, it may be a sign of bone loss throughout the body. This is particularly true when calcium intake has been limited.

Question: Why does bone loss occur during pregnancy?

Answer: The developing fetus accumulates about 30,000 milligrams (about an ounce) of calcium to build its own skeleton. That's a large amount of calcium that must be transferred from the mother's body.

In addition, during breast-feeding, 300 to 400 milligrams of calcium are lost from the body daily in breast milk. In fact, a woman breast-feeding twins can lose as much as 1,000 milligrams of calcium daily through milk production alone.

Q: Do pregnancy and breast-feeding affect long-term bone health?

A: Given the substantial demands on calcium during pregnancy and breast-feeding, 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 and retaining calcium. Even with these adjustments, some bone loss is typical during the last months of pregnancy.

During breast-feeding, additional bone loss occurs, even if the mother has a high calcium intake. After weaning, however, bones generally increase their uptake of calcium and restore bone minerals back to pre-pregnancy levels if adequate calcium is present in a balanced diet.

Q: Can bone loss during pregnancy be a problem?

A: Although it is uncommon, some women have experienced low bone density and bone fractures during or shortly after pregnancy or during breast-feeding. Little is known about the causes of these rare occurrences, but they may be related to low bone density at the start of pregnancy. If bone density is too low, 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.

Q: How does teen pregnancy affect bones?

A: A pregnant teenager already has high calcium needs for her own skeletal development. Consequently, there is concern that the demands of fetal development could prevent the accumulation of peak bone mass for the teen mother. This concern is controversial, but provides extra reasons to encourage overall good nutrition and especially adequate calcium intake.

The bottom line is that a woman's bones are designed to handle the demands of pregnancy as long as her diet has an adequate supply of all nutrients (especially calcium).