The damaging effect of diethylstilboestrol and allyloestrenol in the chick embryo.

After diethylstilboestrol (DES) but in particular after allyloestrenol (AE) treatment, an increased mortality of chick embryos was observed. After DES-treatment a glandular-cystic hyperplasia of the oviduct, persistence and hypertrophy of the right ovary, and pseudohermaphroditism occurred. AE caused rectal and ureteral disorders. Although there are principal differences in sexual differentiation between mammals and birds, our results suggest that the use of AE for the protection of human pregnancies requires caution.