In a letter in response to our paper, Williams and DeSesso questioned why a significant weight gain in arsenic (As)-exposed offspring was found in our study but not in others ( Markowski et al. 2011 ; Markowski et al. 2012 ; Tokar et al. 2010 ; Waalkes et al. 2003 ; Waalkes et al. 2004 ; Waalkes et al. 2006 ). In addition, they point out that early onset of vaginal opening in response to gestational As exposure was not observed by Markowski et al. (2012) or Gandhi et al. (2012) . As we mentioned in the Discussion section of our paper, some of the results under our exposure scheme do not recapitulate those observed in other studies.