Objective: To determine the ability of the hypo-osmotic swelling test to select viable sperm from nonmotile sperm samples for intracytoplasmic sperm injection (ICSI).
Design: Nonrandomized, sequential comparative study.
Patients: Thirteen couples enrolled in our ICSI program had 16 cycles in which sperm preparations with 0% motility were obtained. Five cycles used cryopreserved epididymal sperm with complete asthenozoospermia.
Interventions: In eight cycles, the semen samples were washed through a Percoll gradient and sperm were selected randomly for ICSI. In another eight cycles, the washed sperm were placed in a hypo-osmotic solution (75 mM fructose; 25 mM sodium citrate dihydrate) and the sperm with curled tails taken up with the microinjection needle, rinsed, and used ICSI.
Main outcome measures: Fertilization rate per oocyte injected as determined by the presence of two pronuclei at 18 hours after retrieval and embryo cleavage rate per oocyte injected at 48 hours after retrieval.
Results: With random sperm injection, the fertilization and cleavage rates were 26% and 23%, respectively. In contrast, after injection of sperm selected using the hypo-osmotic swelling test, fertilization and cleavage rates were significantly greater (43% and 39%, respectively). There were three pregnancies in the eight cycles with the hypo-osmotic swelling test-selected sperm, including two from frozen epididymal sperm.
Conclusion: Based on these preliminary observations, we believe that the hypo-osmotic swelling test will prove to be valuable for increasing fertilization and cleavage rates and pregnancy rates in ICSI cycles where no motile sperm are recovered.