Lead exposure before pregnancy reduces birth weight and length

Millions of women of child-bearing age have substantial bone lead stores due to lead exposure as children. We studied the effects of lead exposure of rats at an early age on fetal development during a subsequent pregnancy. Five-week-old female SD rats were given 250 mg/L of lead as the acetate in their drinking water for 5 weeks; controls received equimolar sodium acetate. This was followed by a one month latency period without lead exposure prior to mating. Pregnant rats (n=37) were randomly assigned to diets with a deficient (0.1%) or normal (0.5%) calcium content during pregnancy. A total of 345 pups were delivered alive. Lead-exposed dams and their pups had significantly higher blood lead concentrations than controls, but the concentrations were in the range of those found in many pregnant women. Pups born to lead-exposed dams had significantly (p<0.0001) lower mean ± SE birth weights (6.32 ± 0.05 vs. 6.80 ± 0.05 g) and birth lengths (52.8± 0.2 vs. 53.9 ± 0.2 mm) than controls. Dietary calcium did not influence in utero growth. Stepwise regression analysis demonstrated that greater litter size and female gender were significantly (p <0.0001) associated with reduced pup birth weight and length. However, lead exposure ending well before pregnancy remained significantly (p<0.0001) associated with reduced birth weight and length even after inclusion of litter size, pup gender, and dam weight gain during pregnancy in the regression analysis.