- Sperm stimulants can improve fertilization rates in male-factor cases undergoing IVF to the same extent as micromanipulation by partial zona dissection (PZD) or subzonal sperm insemination (SUZI): a randomized controlled study. Edirisinghe, W.R., Junk, S., Yovich, J.M., Bootsma, B., Yovich, J.L. J. Assist. Reprod. Genet. (1995)