Swan et al. measured 9 metabolites of phthalates in the urine of the mothers in their study. These metabolites are the chemical forms to which phthalates are converted by chemical processes once they enter the human body. The original form--i.e., the phthalate molecule that entered the body as the result of an exposure, is called the parent compound.

Based on current understanding of what happens to phthalates in human bodies, the 9 metabolites originated from 7 different parent compounds, i.e., 7 different types of phthalates. Each of these 7 is manufactured and used in various consumer or industrial processes. To understand the path of exposure, it is necessary to know which parent compound produces which metabolite. That is shown in the table below for each of the phthalate metabolites Swan et al. studied.