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Current evidence is reassuring overall: the American Society for Reproductive Medicine (ASRM) says there does not appear to be an increased risk of breast cancer associated with assisted reproductive technology (ART), which includes IVF. That is not proof of zero risk for every person or treatment history. ASRM separately advises avoiding prolonged clomiphene use beyond 10 cycles; anyone taking fertility medication should discuss their plan with their prescribing clinician rather than changing it on their own.
What ASRM says about breast cancer and fertility treatment
In its 2024 guideline, ASRM recommends informing women that “there does not appear to be an increased risk of breast cancer associated with ART treatments.” It also advises that prolonged clomiphene use—more than 10 cycles—should be avoided. The clomiphene caution is specific; it should not be generalized into a claim that all fertility medicines carry the same risk.
ART, including IVF, is distinct from ovulation-induction medicines such as clomiphene. The guideline’s reassuring conclusion concerns ART overall; it does not guarantee that every individual regimen or exposure history carries no risk. [ASRM, Fertility drugs and cancer: a guideline (2024)]
What studies have found—and what the numbers mean
ASRM’s review found that most studies and all systematic reviews and meta-analyses it considered reported no significant increase, or a decrease, in breast cancer risk. The evidence was not unanimous: one intermediate-quality study reported an increase. A meta-analysis of 20 studies, as summarized by ASRM, found no overall association between hormonal infertility treatments and increased breast cancer risk. [ASRM guideline (2024)]
#1 Best Overall
Some cohort estimates help show the scale and limits of the evidence. In a large cohort summarized by ASRM, IVF compared with no treatment among women with infertility was not associated with a statistically significant increase (hazard ratio 1.10; 95% confidence interval 0.88–1.36). A cohort with more than 30 years of follow-up found no association between ever-use of clomiphene and breast cancer (HR 1.05; 95% CI 0.90–1.22), or gonadotropin use and breast cancer (HR 1.14; 95% CI 0.89–1.44). These are relative estimates from specific studies, not predictions of an individual’s absolute risk, and the cohort studies were not conducted by ASRM. [ASRM guideline (2024)]
Why it is difficult to establish cause and effect
Comparisons between people who receive fertility treatment and those who do not can be affected by underlying differences. Infertility itself, endometriosis and other related factors may influence cancer risk, making it difficult to separate the effects of a treatment from the factors that led to treatment. ASRM also identifies limitations in the evidence, including imperfect control groups, recall bias, failure to account for cancer risk factors associated with infertility, and limited long-term follow-up. [ASRM guideline (2024)]
Timing adds another complication: cancer may be diagnosed years after treatment, while many relevant cancers are uncommon. Long follow-up is therefore important, and even long-running observational studies cannot establish that a treatment caused—or could never contribute to—an outcome.
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What the guideline covers and when it was published
ASRM’s 2024 update identified 1,077 articles and included 52 studies. Its literature search covered publications through November 30, 2022. The guideline is a substantial review, but its stated conclusion reflects evidence available through that search cutoff; it does not by itself establish whether later studies changed the picture. [ASRM guideline (2024)]
Quick Recap
What to do if you are considering or taking fertility medication
- Ask your fertility clinician which treatment category and medication are part of your plan, and how many cycles are intended.
- If clomiphene is being considered for more than 10 cycles, discuss ASRM’s recommendation with the prescribing clinician.
- Share relevant personal and family history, including prior breast conditions or cancers, with your fertility clinician and breast-care clinician when appropriate.
- Do not stop, start, or change a prescribed treatment based on a general article; make medication decisions with your clinician.
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