DRINKING-WATER SOURCE AND REPRODUCTIVE OUTCOMES IN SPRAGUE-DAWLEY RATS

As part of our work on the influence of water source on reproductive o utcome, Sprague-Dawley rats were randomized to tap water, bottled wate r, or deionized water treatment groups, utilizing 160 animals per trea tment; animals received the water prior to and during pregnancy, Rats were shipped in four batches (A-D), Batch effects were seen for severa l reproductive parameters, Because the tap water supply was interrupte d by an earthquake resulting in an unbalanced design, primary analyses utilized only batches C and D, which included most of the tap water-t reated rats, A treatment effect with respect to resorption frequency w as seen that was marginally significant using a fixed-effects analysis of variance (P = 0.053), but not when batch was entered as a random e ffect (P = 0.36), The data were modeled by logistic regression, contro lling for batch, litter size, and batch-treatment interaction, The odd s ratio comparing tap to bottled water was 1.8 (95% CI 1.0 to 3.3, P = 0,05), which was similar to the epidemiologic result that prompted th is study, The magnitude of this association varied by batch, and the d ifference in resorption frequency was within the range of variation se en for control animals, Although these findings do not justify public health action at this time, further investigation is warranted.