Reproductive toxicity has many unique and challenging differences from toxicity to other systems. Whereas other forms of environmental toxicity typically involve development of disease in an exposed individual, because reproduction requires interaction between two individuals, reproductive toxicity will be expressed within a reproductive unit, or couple. This unique, couple- dependent aspect, although obvious, makes reproductive toxicology distinct. For example, it is ppossiblethat exposure to a toxicant by one member of a reproductive couple (e.g., the male) will be manifest by an adverse reproductive outcome in the other member of the couple (e.g., increased frequency of spontaneous abortion). Any attempt to deal with environmental causes of reproductive toxicity must address the couple-specific aspect.
There are other unique aspects that reflect the challenges of reproductive toxicology. Unlike renal, cardiac or pulmonary function, reproductive function occurs intermittently. This means that occupational exposures can interfere with reproduction but go unnoticed during periods when fertility is not desired. This intermittent characteristic can make the identification of a reproductive toxicant in humans more difficult. Another unique characteristic of reproduction, which follows directly from the consideration above, is that complete assessment of the functional integrity of the reproductive system requires that the couple attempt pregnancy.