Treatment of sperm to predetermine sex

Abstract

There are countless reports of “success”, and occasionally of “failure”, to isolate populations of sperm enriched for either X-chromosome bearing sperm or Y-chromosome bearing sperm (hereafter called X-sperm and Y-sperm), or to induce a skewed sex ratio at birth. Unfortunately, most reports are unreliable because the experiment contained inadequate replication, and thus was destined to be inconclusive; used questionable laboratory procedures to evaluate success; or some data were unavailable or were excluded. Furthermore, failures usually are not reported. Specific and statistically robust laboratory tests to evaluate the ratio of X- to Y-sperm in starting and isolated fractions now are available. This should facilitate progress, provided valid experiments are conducted. Ultimately, efficacy of a procedure for altering sex ratio at birth must be established. Presently, only the use of columns of human serum albumin for treatment of human sperm appears to be successful. However, flow sorting may be applicable when only a few doses of sperm are needed for in vitro fertilization or artificial insemination, and reduced fertility is acceptable. Development of a technique for conveniently isolating large populations of cells highly enriched for either X- or Y-sperm, of normal fertility, or for differentially blocking fertilizing capacity of one type of sperm remains an intellectual challenge.