Background: Coitus interruptus, a common contraceptive method, has a high failure rate. Two reasons have been proposed for this: delayed withdrawal after ejaculation and presence of sperm in the pre-ejaculatory fluid.
Objective: To determine whether sperm was present in the pre-ejaculatory fluid of healthy males.
Material and Method: A total of 42 healthy Thai men were enrolled in the study between August 1, 2009 and November 30,
2009 at the Department of Obstetrics and Gynecology, Rajavithi Hospital. They were asked to collect pre-ejaculatory fluid smears in two glass slides and then deposit a semen sample in a plastic bottle after masturbation. Microscopic examination of wet and air-dried preparations and routine semen analyses were done consecutively in the human genetics laboratory.
Results: Actively mobile sperm were found in 16.7% (7/42 cases) of the pre-ejaculatory penile secretions of subjects whose
sperm counts were 2 in 2 cases, 3 in 3 cases and 4 per high power field in the other 2 cases of positive sperm. Semen analyses were normal in 41/42 volunteers (97.6%); there was one case of oligospermia (14x106/ml).
Conclusion: Actively mobile sperm were discovered in the pre-ejaculatory fluid of 16.7% of healthy men.

Keywords: Coitus interruptus, Sperm, Pre-ejaculatory fluid, Thai male