Scientists warn that the seats could damage sperm production by raising men's temperature to unhealthy levels.
An optimal temperature of between 35 and 36 degree Celsius is needed to produce healthy sperm. This is one reason why the testicles hang outside the main part of the body.
To test whether heated car seats might be raising scrotal temperatures above this threshold, German researchers colleagues fitted temperature sensors to the scrotums of 30 healthy men, who then sat on a heated car seat for 90 minutes, reports New Scientist.
According to the NZPA, in another study published in the journal Fertility and Sterility, sperm samples from 32 men were split into two groups, with one sample group set up just 2.5 centimetres away from an 850 MHz cellphone, almost the the same distance from the pocket to the men's scrotum.
The study, which was led by the director of the Center for Reproductive Medicine, Ashok Agarwal, revealed that semen exposed to cellphone emissions lowered the ability of the sperm to move and swim and there was a reduced percentage of live sperm.
Investigations into the heated car seats were based around the ideal temperature for sperm production being one to two degrees celsius lower than the core body temperature of 37C.
After an hour on the seat, the scrotal temperatures of the men were an average of 37.3C with one reaching 39.7C compared to 36.7C for men on unheated seats.