The rank order of women's urine concentrations was similar over time. Fig. 1 shows the concentrations of BDCPP and DPP measured during the 18th week (average) and 28th week of pregnancy and shortly after their child's birth (one woman was missing a sample after the birth). Examining temporal variability in BDCPP and DPP during the 18th week of pregnancy using ICCs, we observed moderate to strong reliability (Table 2) (Rosner, 2000). ICCs calculated over the entire course of pregnancy were slightly lower than those for samples taken over one week but results also suggest moderate reliability over time for urinary metabolites. In general, correcting for urine dilution using specific gravity decreased reliability estimates slightly.