Incidence and implications of altered semen quality on family planning.

Alterations in the expression of the human genome, or interference with its products, can be induced in the male reproductive system by chemicals mimicking or antagonizing naturally occurring hormones. Opportunities exist for disruption at the hypothalamus, pituitary and testis levels. Recent concerns generated by the increased incidence of testicular cancer, congenital anomalies of the male genitalia and possible alterations in human semen quality have been linked to the environment. The report by Carlsen in 1992 [1] suggested that semen quality has deteriorated over the past six decades. More recent reports suggest that the decline may be globally non-uniform and regional in nature. The effects of any such declines upon overall pregnancy rates are generally unknown, although some studies have attempted to address them. A preliminary review of the impact of a small decrease in sperm concentrations suggests that a directly measurable reduction in fecundity does not occur, but that future problems could be anticipated. Decrements in semen quality will alter the epidemiological probabilities of pregnancy due to coitus on different cycle days and may thereby change the duration of the fertile time. Current understanding of the implications of altered semen quality on relative fertility is not sufficient to change our current teaching and practice of NFP.