Hereditary Cancer Variants and Family Planning: What Your Options Are

By Amanda Shrewsbury, MS, CGC

If you carry a hereditary cancer variant and you are thinking about having children, one of the first questions that may come up is whether your variant changes what building a family looks like. The reassuring starting point is that carrying a variant does not stand in the way of having the family you want, but it does provide important information for family planning.

Carrying a variant in a gene like BRCA1, BRCA2, or one of the Lynch syndrome genes is common, and it is not a flaw or a barrier. Many people who carry these variants go on to have children, often without any medical intervention at all. What a variant does offer is information: some understanding of how the variant might be passed on, and in certain situations, a reason to consider testing a partner or donor as well. This post walks through both.

There are really two separate questions woven through this topic. The first is the familiar one: could my child inherit my variant, and what are my options? The second is less well known but just as important: could my variant, combined with a variant my partner carries, have implications for my child's health in a different way? We will take them in turn.

Could my child inherit my genetic variant?

Most hereditary cancer variants are inherited in an autosomal dominant pattern. In practical terms, this means that each child of a person who carries the variant has a 50 percent chance of inheriting it. This is true regardless of the child's sex, and it is true whether the variant is passed down from the mother or the father.

It is worth sitting with what inheriting the variant does and does not mean. A child who inherits a hereditary cancer variant is not born with cancer and is not guaranteed to develop it. They inherit an elevated risk, one that is typically managed in adulthood through screening and prevention, the same way you may be managing yours now. That is why, for most hereditary cancer syndromes, the recommendation is not to test children, but to wait until adulthood when the information becomes actionable. However, it is important to know that there are some exceptions to this. Our post on the right age for genetic testing covers this in more detail.

What are my options if I carry a variant?

For people who carry a hereditary cancer variant and want to understand their options, the question is really what, if anything, you want to do about the variant as you build your family. Families are built in many ways, including with the help of donor gametes, IVF, and surrogacy, and a genetic counselor works with people across all of these paths. The options discussed are framed around the variant itself. These options are not required, and there is no "right choice" - they are simply options.

Preimplantation genetic testing (PGT-M). For those who want to reduce the chance of passing on a specific variant, PGT-M is an option that works alongside in vitro fertilization (IVF). Embryos created through IVF can be tested for the specific familial variant, and embryos without it can be selected for transfer. In a scenario where all of the embryos carry the variant, you can have discussions with your care team about selecting the lower-risk embryos, for instance, selecting a male embryo with a BRCA1 variant rather than a female embryo with a BRCA1 variant, since the associated cancer risks differ by sex. PGT-M is one option, never a requirement, and choosing not to pursue it is an equally valid decision.

Prenatal testing. During a pregnancy, testing can determine whether the fetus has inherited the familial variant. Some people use this information to prepare; others prefer not to test prenatally for an adult-onset condition. Both are reasonable to consider, and to discuss with your care team.

Not testing for the variant. Many people who carry a hereditary cancer variant choose not to pursue any testing related to it during family planning, understanding that a child who inherits the variant inherits an adult-onset risk that can be managed with appropriate screening later in life. This is a common and completely valid choice.

The point of laying these out is not to suggest that carrying a variant obligates anyone to do anything differently. It is simply to discuss the options that exist, and understanding them lets you make the choice that fits your values.

What is a carrier, and why does it matter for some cancer genes?

Here is where the second, less familiar question comes in.

A carrier is a person who has one variant in a gene that is associated with a recessive condition, meaning a condition that only develops when a person has two variants in that gene, one inherited from each parent. Being a carrier of a single variant usually does not cause the recessive condition itself.

This matters for family planning because several hereditary cancer genes are also associated with recessive conditions. In other words, the same gene that confers an adult-onset cancer risk when one variant is present can, in some cases, cause a serious childhood condition when two variants are present, one from each parent. This is one of the most important reasons that reproductive genetic counseling is worthwhile for people who carry these variants.

The genes where this matters

A handful of hereditary cancer genes have this dual character. Here are the most relevant, described briefly.

BRCA1, BRCA2, PALB2, BRIP1, and RAD51C (the Fanconi anemia pathway genes). Several hereditary breast and ovarian cancer genes are part of what is called the Fanconi anemia pathway, a group of genes that work together to repair DNA. When a person carries a single pathogenic variant in one of these genes, the association is with adult-onset cancer risk: BRCA1 and BRCA2 with hereditary breast, ovarian, and other cancers; PALB2 with breast and pancreatic cancer; and BRIP1 and RAD51C primarily with ovarian cancer. When a child inherits two pathogenic variants in one of these genes, one from each parent, the result can be Fanconi anemia, a serious condition involving bone marrow failure and a high risk of childhood cancers (Nalepa & Clapp, 2018). BRCA2 (associated with FANCD1) and PALB2 (associated with FANCN) are the most established of these, and two variants in BRCA1 (associated with FANCS), BRIP1 (associated with FANCJ), and RAD51C (associated with FANCO) have also been associated with Fanconi anemia or Fanconi anemia-like presentations.

The Lynch syndrome genes (MLH1, MSH2, MSH6, PMS2, and EPCAM). A single variant in one of these genes causes Lynch syndrome, an adult-onset condition associated with colorectal, endometrial, and other cancers. Four of these (MLH1, MSH2, MSH6, and PMS2) are known as mismatch repair genes, and when a child inherits two variants in the same mismatch repair gene, one from each parent, the result can be constitutional mismatch repair deficiency (CMMRD), a severe childhood cancer syndrome (Wimmer et al., 2014). As one way to picture it: when a child has CMMRD, it usually means both parents carry a Lynch syndrome variant.

ATM. A single ATM variant is associated with an elevated risk of breast, pancreatic, and other cancers in adulthood. When a child inherits two ATM variants, one from each parent, the result can be ataxia-telangiectasia, a childhood-onset condition affecting movement, the immune system, and cancer risk (Hall et al., 2021).

Lower-cancer-risk carrier genes. Some genes that appear on hereditary cancer panels carry little or no personal cancer risk when a single variant is present, but are associated with recessive conditions. MUTYH is one example: there is not enough evidence to suggest a single variant is associated with increased colorectal cancer risk, but two variants cause MUTYH-associated polyposis, a condition involving numerous colon polyps and elevated risks of colorectal and other cancers (Nielsen et al., 2012). CFTR, the gene associated with cystic fibrosis, is another gene where carrier status has reproductive implications, and it is a standard part of reproductive carrier screening.

If two people carry a variant, what does it mean for the child?

This is the most important point in the entire post, and it is worth being precise, because the precision is both reassuring and accurate.

If two people each carry a variant in the same recessive-associated gene, each child has three possible outcomes. These two people are whoever contributes the egg and the sperm, whether that is you and a partner, you and a donor, or a donor and a partner, so the same logic applies no matter how a family is built.

The child inherits neither variant. They are not a carrier, and they do not have the elevated adult-onset cancer risk associated with that gene.
The child inherits one variant. This is the key point. The child does not have the recessive childhood condition. Fanconi anemia, CMMRD, and ataxia-telangiectasia all require two variants, so a child with only one variant does not have these conditions. However, that child is a carrier, and they do carry the associated adult-onset cancer risk. A single BRCA2 variant still carries hereditary cancer risk, a single Lynch gene variant still causes Lynch syndrome, and a single ATM variant still carries its associated risk.
The child inherits both variants. Only in this case does the child have the recessive condition.

The takeaway is twofold. First, inheriting a single variant does not mean a child has the severe recessive condition, which is genuinely reassuring. Second, inheriting a single variant does still carry the adult-onset cancer risk, which matters for that child's care in adulthood and for their own future family planning. These two truths sit side by side, and holding both is what makes this information significant to note and understand.

Why testing your partner or donor may matter

This is the practical reason all of the above matters. If you carry a variant in a gene associated with a recessive condition, the question of whether your child could have that recessive condition depends on whether your reproductive partner, or your sperm or egg donor, also carries a variant in the same gene.

If your partner or donor does not carry a variant in that gene, your child cannot inherit two variants, and the recessive condition is not a concern (though a child could still inherit your single variant and its adult-onset cancer risk). If your partner or donor does carry a variant in the same gene, then testing gives you information you would want to have, and a genetic counselor can walk through what it means and what options exist.

This is why, when someone tests positive for a variant in a gene with a recessive disease association, a genetic counselor may recommend testing the reproductive partner or donor. It is not about alarm. It is about having a complete picture before making family planning decisions.

Carrier screening panels versus hereditary cancer testing

There is a common point of confusion worth clearing up, because it affects what people think they already know about their own genes.

Reproductive carrier screening panels and hereditary cancer testing are two different tests with two different purposes. Carrier screening panels are designed to identify carrier status for recessive, typically childhood-onset conditions such as cystic fibrosis, spinal muscular atrophy, and sickle cell disease. Hereditary cancer testing is designed to identify variants that typically raise the risk of adult-onset cancers, but there are some variants associated with childhood-onset cancer risk.

Because of this difference in purpose, adult-onset hereditary cancer genes like BRCA1 and BRCA2 are generally not included on standard reproductive carrier screening panels. This means that a "negative" or "you are not a carrier" result from a reproductive carrier screen generally does not tell you anything about your hereditary cancer risk, because those genes were most likely never tested. If you want to understand your hereditary cancer risk, that requires dedicated hereditary cancer testing.

There is one notable exception. ATM, because of its association with the recessive condition ataxia-telangiectasia, sometimes does appear on carrier screening panels, even though it is also an adult-onset cancer gene. It sits in both worlds. This is the exception that proves how distinct these two categories usually are.

How a genetic counselor helps

A genetic counselor is the right person to help you navigate all of this. They can explain how your specific variant is inherited, lay out the reproductive options without bias, determine whether testing your partner or donor is worthwhile, and coordinate that testing if you choose to pursue it. The goal is never to tell you what to do. It is to make sure you have accurate, complete information so that whatever you decide is fully your own choice.