Reference summary — not medical advice or a personal risk estimate.
Diethylstilbestrol (DES)
Quick answer
Classified as Group 1 — carcinogenic to humans, based on sufficient evidence in humans. Historical medication. Prescribed to some pregnant women between roughly 1940 and the early 1970s; no longer prescribed for pregnancy anywhere. Some exposures persist in adult children and grandchildren of those who took it.
Summary
A synthetic estrogen given to some pregnant women between 1940 and 1971. Daughters and granddaughters of users face increased cancer risk.
Detail
DES is Group 1 with sufficient evidence for breast cancer (in women who took it) and for vagina/cervix clear-cell carcinoma in daughters exposed in utero. DES is no longer prescribed for pregnancy in any country; most exposures are historical, from prescriptions written between roughly 1940 and the early 1970s.
What's not established
This classification is based on sufficient evidence in humans that this factor can cause cancer. It does not establish a safe exposure threshold, your personal risk, or how this factor's risk compares in size to other Group 1 agents — hazard classifications are not ranked by magnitude.
Regional relevance
historical
Evidence sources
Every claim on this page traces back to one of these. Click through to read the primary document yourself.
Primary sources
NCI
NCI — Risk Factors: Hormones
IARC
IARC Monographs — Classifications by Cancer Site, Vols 1–140
Supporting sources
ACS
ACS — Known and Probable Human Carcinogens
NTP
NTP — Report on Carcinogens (US National Toxicology Program)
Last reviewed: October 2026
Official reference list
A government list some readers use alongside the primary evidence. Meyron is not affiliated with it. A chemical being listed does not by itself describe a risk from any particular product.
- California Prop 65 list
State of California's list of chemicals known to cause cancer or reproductive harm.