Hypo-Osmotic Swelling Test and Male Factor

Abstract

For over 30 years, defects of the functional integrity of the sperm membrane, as evidenced by a low hypo-osmotic swelling test when evaluating the semen analysis, are not only associated with male infertility (even with sperm that otherwise seem normal), but unless corrected, successful intrauterine pregnancies will rarely ensue. This defect, interestingly, does not impair fertilization of the oocyte, but instead, prevents a normal-appearing embryo from successfully implanting. The frequency in infertile couples increases with advancing age of the male, ranging from 5% in younger males to 25% in men in their late forties or early fifties. It seems to be related to a toxic protein added to the sperm as they traverse the ejaculatory ducts. The defect is very correctable, either by treating the sperm with the protein digestive enzyme chymotrypsin prior to intrauterine insemination and avoidance of unprotected sex prior to ovulation, or in vitro fertilization with intracytoplasmic sperm injection. Unfortunately, this very inexpensive, easy-to-perform test is rarely performed by the large majority of physicians treating infertility. The purpose of this manuscript is to hopefully rekindle interest within the infertility community to add this test to the standard semen analysis.