Contaminants exercise an influence on different levels of reproduction, resulting in disturbances of the cycle, abortion and diverse complications during pregnancy among women, whereas, in the case of men, alterations of the spermiogram have been observed. Numerous unfavourable influences on reproduction are known from toxins such as alcohol, cigarettes and caffeine. By means of a survey of references and own results, these secondary effects are demonstrated in order to warn couples of the serious consequences with regard to the abuse of toxins, e.g. coffee, tobacco etc., when seeking advice in questions of infertility and pregnancy.