Sperm and barrier contraception. Computer illustration of a group of sperm cells (spermatozoa) swimming inside a barrier contraceptive device such as a condom. Sperm are the male haploid reproductive cells (gametes). A sperm fuses with a female ovum (egg) during fertilisation to form a diploid zygote, which will develop into a foetus. Barrier contraceptives help to prevent pregnancy by physically preventing the sperm from entering the uterus (womb) and reaching the egg.