Associations of parity, breast-feeding, and birth control pills with lumbar spine and femoral neck bone densities

Am J Obstet Gynecol. 1988 Aug;159(2):318-22. doi: 10.1016/s0002-9378(88)80075-9.


The relationships between parity, breast-feeding, and the use of birth control pills and the bone densities of the lumbar spine and the femoral neck, measured by dual-photon densitometry, were studied in normal women. Femoral neck density was found to decrease by 1.1% per live-birth, whereas lumbar spine density showed no significant association with parity. Breast-feeding was found to increase lumbar spine density by 1.5% per breast-fed child, whereas femoral neck density was not significantly correlated. No significant relationships between the use of birth control pills and the bone densities were found.

PIP: Researchers measured the bone densities of the lumbar spine and the femoral neck using dual-photon densitometry in 352 normal women (range: 21 to 79 years old) in order to study the relationship between the bone densities and parity, breast feeding, and the use of oral contraceptives (OCs). Since the most common manifestations of osteoporosis, a bone disease most often afflicting elderly women, include spinal compression factors and fractures of the femoral neck, the scientists wanted to learn if parity, breast feeding, and the use of OCs increase the risk of acquiring this chronic bone disease. Femoral neck density decreased 1.1% per live birth (p = .039), whereas there was no significant difference between parity and lumbar spine density (p [alpha] = .16; p [beta] = 0). Lumbar spine density increased by 1.5% per breast-fed infant (p = .008), while no significant correlation existed between femoral neck density and breast feeding. Furthermore, researchers observed no significant relationships between OC use and both bone densities. In conclusion, since pregnancy and lactation involve complex hormonal and nonhormonal changes, the researchers find it difficult to pinpoint the mechanisms of these effects.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Breast Feeding*
  • Contraceptives, Oral / administration & dosage*
  • Densitometry / methods
  • Female
  • Femur Neck / anatomy & histology*
  • Humans
  • Lumbar Vertebrae / anatomy & histology*
  • Middle Aged
  • Minerals*
  • Parity*
  • Time Factors


  • Contraceptives, Oral
  • Minerals