Reference summary — not medical advice or a personal risk estimate.
Never having a full-term pregnancy (nulliparity)
Quick answer
Not IARC-classified — this is not a chemical or physical agent IARC rates. Recognized as a cancer risk factor based on observational evidence. Reproductive history. Applies to people who have never carried a pregnancy to full term.
Summary
Women who have never carried a pregnancy to term have a modestly higher lifetime breast and ovarian cancer risk than women who have.
What's not established
This is an observed population association, not a personal risk calculator. It does not establish causation independent of other reproductive and hormonal factors, and it says nothing about the many non-cancer-related reasons people do or do not have children.
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 — Reproductive History and Cancer Risk
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.