The effect of pregnancy and lactation on bone mineral density in fluoride-exposed rats. 
Fluoride increases metabolic turnover of the bone in favour of bone formation.  Excessive intake of fluoride may lead to pathological changes in teeth and bones: dental and skeletal fluorosis.  In this study, we investigated the effect of pregnancy and lactation on bone mineral density (BMD) in fluoride-exposed rats.  Female Wistar rats were given commercially available spring water with 100 ppm fluoride (N = 8), or without addition (N = 8) for 18 weeks.  At 16 weeks of age, four female rats and one male rat were kept in a cage for 5 days; all females were successfully impregnated.  BMD was measured at 16 weeks of age, on the first day postpartum, and at the end of lactation.  Spinal BMD was significantly higher in fluoride-exposed rats than control (P < 0.05), but there were no differences in femoral BMD (P = 0.670).  During pregnancy, spinal BMD and femoral BMD were not significantly changed in fluoride-exposed rats, whereas BMD of the spine was significantly decreased in the control rats (P = 0.013), but not in the femur.  During lactation, BMD was significantly decreased at the two regions compared to initial values (P < 0.05) in both groups.  This study shows that pregnancy has no effect on bone, but lactation has a decreasing effect on BMD in fluoride-exposed rats.