DES (diethylstilbestrol) is a known carcinogen and teratogen. In both animal models and humans, DES causes severe abnormalities to the developing female genital tract. Early in utero, DES changes the appearance and lining characteristics of the developing uterus, cervix and vagina. Normally, these organs develop simultaneously from the Mullerian duct system and differentiate (branch out) into different tissue types based on specific instructions given to them by the supporting soft tissues just beneath them. Normally, the paired embryonic Mullerian ducts fuse into a single uterovaginal tract or canal, the uterine and Fallopian tube mesenchyme (supporting structure) differentiates into inner endometrial and outer myometrial (muscular) layers and there is folding of the tubal endometrial mucosal linings. The vagina develops into a stratified squamous barrier lining.
Finally, there is uterine gland formation that allows for implantation of a fertilized ovum. Under the influence of DES, glandular epithelium or adenosis is found in the vagina, the growth of the upper genital tract is stunted and the inner and outer linings of the uterine body and Fallopian tubes fail to separate. All of these findings are markedly abnormal and have been seen in DES exposed women.
With normal differentiation, a uterus should be fairly distensible, supple and able to receive a newly fertilized ovum (egg). The cervix and vagina are normally not glandular structures and instead provide structure and support during the birth process. DES changes this entire dynamic with wide ranging complications. Instead of having a developing uterus that is later able to accept a fertilized ovum (egg), the uterus of a DES exposed women is hard, less supple, receives a reduced blood flow.
The cervix and vagina can and often develop glands which may in turn become cancerous. Diethylstilbestrol can lead to multiple other abnormalities including endometriosis and scar tissue in the Fallopian tubes with ectopic pregnancy. If exposed in utero to diethylstilbestrol, a woman can expect one or more serious complications during her reproductive life (1).
1. Stillman R.J. In Utero Exposure to Diethylstilbestrol: Adverse Effects on the Reproductive Tract and Reproductive Performance in Male and Female Offspring. Am J. Obstet. & Gynec. 142:902, April 1982.