Effects of prenatal pyrethroid insecticide exposure on the sexual development of rats.

The prenatal effects of exposure to the insecticide cyhalothrin on the sexual maturation and sexual behavior of rats were investigated. Female rats were dermally treated with 1 ml/day of 0.02% (w/v) aqueous cyhalothrin solution or its vehicle throughout pregnancy. This insecticide administration delayed the age of testicle descent but did not modify the age of vaginal opening. In adulthood, both male and female rat sexual behaviors were not different from vehicle-treated animals. It was concluded that prenatal exposure to cyhalothrin can induce alterations in the development of certain physical characteristics of rats which are not correlated with functional deficiencies in the animals' later life.