Purpose of investigation: The effect of different types of textiles on pregnancy was studied in 35 pregnant bitches divided equally into one control and four experimental groups. Methods: During pregnancy, the test groups were dressed in a garment made of either pure polyester, cotton or wool, or of a 50/50% polyester-cotton mix. Serum estradiol 17 B and progesterone were measured before and every 15 days during pregnancy. Electrostatic potential (EP) was assessed on the skin before and after wearing the garment Results: The bitches wearing cotton, wool and polyester-cotton mix as well as five of the seven wearing pure polyester garments had normal serum estradiol and progesterone during pregnancy and produced normal offspring. The remaining two animals of the group wearing pure polyester showed low serum progesterone levels in the first month of pregnancy and had spontaneous abortions Mating was attempted in these two bitches during the subsequent estrous cycle without making them wear polyester garments Serum levels of reproductive hormones were normal and they produced normal offspring. EP was detected on the skin of only the polyester-dressed groups, and was higher in the pure than in the mixed polyester groups. Conclusions: The cause of low serum progesterone and abortion in the two bitches is unknown. Abortion seemed to be due to the low serum progesterone which may have resulted from the injurious effect of EP on the ovarian or placental function.