In utero exposure of mice to diethylstilbestrol alters neonatal ovarian follicle growth and development.

The prenatal exposure of mice to diethylstilbestrol (DES, 10 micrograms/kg on day 15 of gestation) caused both quantitative and structural alterations in ovarian follicles within the neonatal ovary. At birth, control ovaries consisted of small type 1 and 2 ovarian follicles located in the ovarian cortex. By postnatal day 7, ovarian follicle development had advanced to the type 4 stage with larger follicles located within the ovarian medulla. In DES-exposed animals, ovarian follicle maturation was advanced with type 3b and 4 follicles appearing 24 h prior to their appearance in control animals. Also, type 5 ovarian follicles were present on postnatal day 6 in experimental animals but were never seen in control animals. In addition to an alteration in ovarian follicle dynamics, the diameter of individual ovarian follicles was transit time between the various stages of follicular development which results in a greater number of developmentally advanced ovarian follicles being present during neonatal ovarian development. The mechanism by which prenatal exposure to DES alters ovarian follicle dynamics during neonatal development is not known.