Sperm have no idea where they are going and their journey to the egg resembles a demolition derby, according to British scientists.
While one percent of the roughly 300 million sperm released during sex reach the uterus, only about a dozen find the egg.
A joint study by University of Warwick and University of Birmingham researchers found sperm avoid the middle lane of the female reproductive tract, instead crawling along the channel walls, the Daily Mail reported.
In the study, sperm cells were injected into hair thin micro channels.
"When the channel turns sharply, cells leave the corner, continuing ahead until hitting the opposite wall of the channel, with a distribution of departure angles, the latter being modulated by fluid viscosity," the reports said.
"As a consequence of swimming along the corners, the domain occupied by cells becomes essentially one-dimensional.
"This leads to frequent collisions and needs to be accounted for when modelling the behaviour of populations of migratory cells."
Dr Peter Denissenko of the University of Warwick said sperm cells following walls was a case of a "complicated physiological system" obeying simple mechanical rules.
"I study fluids in a variety of environments, but moving to work with live human sperm was quite a change," Dr Denissenko.
"I couldn't resist a laugh the first time I saw sperm cells persistently swerving on tight turns and crashing head-on into the opposite wall."
The findings, published in the Proceedings of the National Academy of Sciences journal, could be used in future innovations to treat infertile couples.
"In basic terms - how do we find the 'Usain Bolt' among the millions of sperm in an ejaculate?" Dr Jackson Kirkman-Brown, from the Birmingham Women's Fertility Centre, said.
"Through research like this we are learning how the good sperm navigate by sending them through mini mazes.
"Previous research from the group indicates that the shape of the sperm head can subtly affect how the sperm swim.
"Combined with this data we believe new methods of selecting sperm, perhaps for quality or even in certain non-human species for sex may become possible."
- Herald Online staff