The short answer
Most cancer predisposition variants pass with a 50% chance to each child. Inheriting one raises risk without guaranteeing cancer. Several reproductive options exist, including PGT-M, and a genetic counselor can walk through all of them without steering you.
Autosomal dominant inheritance means each child has an independent 50% chance of inheriting the variant — it is not a quota across siblings.
Inheriting a variant raises risk; it does not guarantee cancer, and risk levels differ substantially between genes.
Reproductive options include conceiving without testing, PGT-M with IVF, prenatal diagnosis, donor gametes, adoption, and fostering.
PGT-M is technically established for BRCA1, BRCA2 and Lynch syndrome, but requires IVF, is costly, is often uninsured, and does not guarantee a pregnancy.
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The full explanation.
What the inheritance numbers mean
Most cancer predisposition variants are inherited in an autosomal dominant pattern. That means each child of a carrier has a 50% chance of inheriting the variant and a 50% chance of not inheriting it. That figure applies on its own to each child. It is not a quota. Three children can all inherit it, or none can.
Two things often get merged in the middle of the night, and they are worth separating.
Inheriting a variant is not the same as developing cancer. A variant raises risk. It does not schedule an event. Risks vary widely by gene. Take BRCA1 and BRCA2, where more than 60% of women who carry a harmful variant develop breast cancer. Ovarian cancer risk there runs 39% to 58% for BRCA1 and 13% to 29% for BRCA2. Meaningful, but not certain.
A child who inherits it also inherits the knowledge. They would grow up knowing, with access to screening and prevention that did not exist for earlier generations.
Reproductive options exist, and you can ask about them
If you are planning a family, or already have children, there are more paths than people are usually told. A genetic counselor can walk through all of them without steering you toward any:
- Conceiving without testing. Many carriers do exactly this. Adult-onset conditions are generally not tested for in childhood, so a child would decide for themselves as an adult.
- Preimplantation genetic testing for monogenic conditions (PGT-M). Embryos created through IVF are tested for the specific familial variant, and unaffected embryos are transferred. This is technically established for BRCA1, BRCA2, Lynch syndrome and others. It requires IVF. It is expensive, it is not always covered by insurance, and it does not guarantee a pregnancy.
- Prenatal diagnosis during a pregnancy, which raises decisions many people would rather not face.
- Donor eggs or sperm from a donor who does not carry the variant.
- Adoption or fostering.
Professional bodies, including the American Society for Reproductive Medicine, have addressed PGT-M for adult-onset conditions specifically. They regard it as an option families may reasonably consider. It is a choice, not a recommendation.
Testing children
For adult-onset cancer predisposition, testing children is generally deferred until they are old enough to decide for themselves. The reasoning is twofold. Nothing done in childhood would change the outcome. And a result carries lifelong implications the child did not consent to.
Some syndromes are different. A few do warrant testing and surveillance early, including conditions where cancers occur in childhood. Your genetic counselor can tell you which category your family's gene falls into.
Telling children who are already here
There is no single right age. What tends to work is telling in stages. Start with a simple, non-frightening version early: there is something that runs in our family, and doctors know how to watch for it. Add more detail as they can hold it.
Adolescents often already suspect something. Silence rarely reads as protection. More often it reads as fear. Children told gradually tend to absorb it as a fact about their family rather than a shock.
What the fear usually is underneath
The fear of passing something on is rarely about statistics. It is usually a version of not wanting your child to go through what you or your parents went through.
That is worth saying out loud to someone. It could be a genetic counselor, a therapist familiar with hereditary conditions, or a peer support group for your specific syndrome. It does not have to be resolved before you make decisions. And it should not be the only voice in the room when you do.
You did not choose your genome, and you did not design the inheritance. What you can choose is what your family knows and what they are able to do about it.
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Words to know
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Common questions
If I have three children, does that mean one and a half will inherit it?
No. The 50% applies independently to each pregnancy. All three could inherit it, or none could. It works like a coin toss each time, not like dividing a fixed amount.
What is PGT-M?
Preimplantation genetic testing for monogenic conditions. Embryos created through IVF are tested for the specific familial variant, and embryos without it are transferred. It is established for BRCA1, BRCA2, Lynch syndrome and others, but it requires IVF, is expensive, is not always covered, and does not guarantee a pregnancy.
Should I have my children tested now?
For adult-onset cancer predisposition, testing is generally deferred until a child is old enough to decide for themselves, because nothing done in childhood would change the outcome. A few syndromes where cancers occur in childhood are exceptions. Your genetic counselor can say which category applies.
When should I tell my children?
There is no single right age. Telling in stages tends to work — a simple version early, more detail as they can hold it. Adolescents often already sense something, and silence more often reads as fear than as protection.
Is it selfish to have biological children knowing I carry a variant?
That is a values question rather than a medical one, and reasonable people answer it differently. Worth holding alongside it: a child who inherits the variant also inherits knowledge and access to screening that earlier generations did not have.
Questions to ask your doctor
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Written by: Cancer ExplainedSources last checked: 2026-07-30 what this meansLast updated: 2026-08-10Next planned review: 2027-07-30
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How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes. We do not employ clinicians and do not intend to — our work is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and checked line by line against the sources listed on it. That confirms the sources support what the page says. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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