Milk versus TEST-yolk — preincubated sperm; in vitro fertilization outcome

Abstract

Objective: Preincubation of sperm in TEST-yolk medium enhances in vitro fertilization (IVF) outcome. However preincubation of sperm in milk at 5°C enhances the results of sperm penetration assay and hemizona assay. This study was therefore performed to determine the influence of milk on in vitro fertilization rate of human oocytes, as compared with TEST-yolk medium. Study design: Forty-one consecutive couples undergoing an IVF procedure were randomized. Of these 20 couples were admitted for the milk study (group 1) and 21 couples for the TEST-yolk study (group 2). Each ejaculate was Percoll-processed and the sperm pellet was resuspended in 0.5 ml of culture medium. An equal volume of heat-inactivated homogenized cow's milk (95°C, 10 min) was added to sperm suspension from group 1 and an equal volume of TEST-yolk medium was added to sperm suspension from group 2. After 2 h of incubation at 5°C and washing with culture medium at 37°C, oocytes were inseminated. Oocytes from group 1 couples were inseminated with milk-treated spermatozoa and those from group 2 couples with yolk-treated spermatozoa. Oocytes were evaluated for fertilization after 18 h. Results: Sperm preincubated in milk fertilized 75 out of 100 mature oocytes (75%). TEST-yolk-treated sperm fertilized 45 out of 64 mature oocytes (70%). The difference was not statistically significant. Conclusions: Preincubation of spermatozoa in milk, as compared with preincubation in TEST-yolk medium yields a similar IVF outcome, so milk may be a suitable alternative medium for preincubation of spermatozoa to enhance its fertilizing potential.