Osteoporosis

It has been since long assumed that pregnancy and lactation are detrimental to the bone density in women. Apart from the obvious un-logic of this assumption (the survival of the species to be detrimental to the individuals assigned to implement said survival) research shows the assumption to be false. Women who have been pregnant and have been lactating have bone densities similar to or even higher than women who did not do so.  In Japan Kurabayashi et al studied the course of changes in bone mineralization in pregnant and lactating women up to 5-10 years postpartum. Thy found a decrease in bone density towards the end of pregnancy and during lactation, but an increase up to starting levels or more around the time of weaning. These levels stayed at a stable level in the subsequent years. Women with low bone density to start with did not get better levels through lactation. Karlsson et al in Sweden did similar research and found a 5% decrease in bone mineralization during pregnancy and lactation, but were unable to put this onto the account of pregnancy and lactation per se, as too many factors play their roles in the total picture. The acknowledge previous findings of increase bone density up to normal levels after weaning and concur with conclusions that multiple pregnancies and prolonged breastfeeding pose no increased risk for osteoporosis.
Kurabayashi T, Tamura R, Hata Y, Nishijima S, Tsuneki I, Tamura M, Yanase T: Secondary osteoporosis UPDATE. Bone metabolic change and osteoporosis during pregnancy and lactation. Clin Calcium. 2010 May;20(5):672-81.
Karlsson MK, Ahlborg HG, Karlsson C: Pregnancy and lactation are not risk factors for osteoporosis or fractures. Lakartidningen. 2005 Jan 31-Feb 6;102(5):290-3.
Lenora J, Lekamwasam S, Karlsson MK: Effects of multiparity and prolonged breast-feeding on maternal bone mineral density: a community-based cross-sectional study. BMC Womens Health. 2009 Jul 1;9:19.