Under the Microscope: Reproductive Choices in CMT

By Katherine Forsey, PhD | CMTA Chief Research Officer

A patient-friendly overview of family planning options for people living with Charcot-Marie-Tooth disease (CMT). A qualified Genetics Counsellor should be consulted for a fuller understanding of the reproductive choices available.

Introduction

Choosing to start a family when you or your partner has Charcot-Marie-Tooth disease (CMT) can bring excitement and questions. Understanding the chances of passing CMT on to children and the reproductive options available empowers individuals to make informed choices. This article does not advocate for any particular option; the choices available to each individual will depend on geographic location, access restrictions, and personal circumstances. 

Understanding Inheritance in CMT

Different CMT subtypes are passed on in different ways:

Autosomal dominant: The most common CMT subtype, CMT1A (PMP22 gene duplication), is autosomal dominant, meaning a child has a 50% chance of inheriting CMT if one parent has this subtype. Other autosomal dominant subtypes include CMT1B (MPZ gene) and CMT2A (MFN2 gene). If both parents have an autosomal dominant type of CMT (which is very uncommon), the chance of passing on CMT will be 75%, and each child will have the same chance.

Autosomal recessive: In autosomal recessive CMT, both parents must carry the altered gene for their child to be affected. Each pregnancy carries a 25% chance of an affected child, a 50% chance of a carrier, and a 25% chance of an unaffected child. Example autosomal recessive subtypes include CMT4A (GDAP1 gene) and CMT4C (SH3TC2 gene).

X-Linked: Some CMT subtypes, for example CMTX1 (aka CMT1X or CMTX) (GJB1 gene), are X-linked, meaning the altered gene is on the X chromosome, one of the two chromosomes that determine a child’s sex. When mom has this CMT subtype, each child has a 50% chance of inheriting CMT. When dad has CMTX1, however, his sons will not inherit but every daughter will. How severely a child is affected depends on their sex: males (XY) who inherit the altered X are typically affected, while females (XX) typically have much milder symptoms because they also inherit a second, healthy X chromosome.

De novo mutations: Occasionally, a CMT-causing mutation occurs randomly, spontaneously, at or shortly after conception. When this happens, it’s called a de novo (new) mutation. This means the child has CMT without having inherited it from a parent. De novo cases are rare but important to recognize for the child’s future family planning options.

A genetic counselor can explain your specific CMT subtype (if known) or arrange for you to undergo genetic testing to attempt to discover it. Once the subtype is known, the inheritance pattern and your reproductive options can be explained more accurately.

Visit our CMT Inheritance page to learn more.

Reproductive Options

Natural Conception, the Right to Choose, Prenatal Testing

Some parents who have CMT choose to conceive naturally and not find out if the unborn child has CMT. That is a valid choice, and a parent’s right to choose should always be respected. For those who wish to find out, prenatal tests undertaken early in pregnancy, like chorionic villus sampling (CVS) or amniocentesis, can determine if the unborn child has inherited the altered CMT gene. Prenatal testing laws and policies vary by municipality, each type of test comes with its own risks, and the tests themselves do not stop CMT from being passed on.

IVF with PGT-M

Preventing CMT from being passed on is possible through a process called in vitro fertilization (IVF) with additional genetic testing known as preimplantation genetic diagnosis (PGD). The parents’ (or donor) sperm and eggs are mixed in a dish, and the resultant fertilized egg divides into multiple cells. One (or a small number) of these cells are then removed and tested for CMT. The embryos without CMT can be selected and placed in the uterus to grow to full term. This greatly reduces the chance of passing on CMT. The process can be expensive, physically demanding, and is not available everywhere.

Using Donor Eggs or Sperm

Using donor sperm or eggs without the CMT variant for insemination or IVF, respectively, removes the genetic risk of CMT inheritance, but it would be important to check if the donors have been screened for CMT, as this is not always done as a standard because CMT is such a rare disease.

Adoption and Foster-to-Adopt

Adoption offers a meaningful way to build a family while completely avoiding CMT inheritance. However, it is important to recognize that some parents in our community have adopted children who have CMT. The full genetic background of adopted children is not usually known, and family history information can be missing or difficult to obtain; this can often lead to a longer diagnosis journey. The adoption process and waiting times differ depending on region and agency.

Emotional and Practical Considerations

Every choice comes with its own mix of hopes, practicalities, and emotions. Genetic counselors, fertility specialists, and support communities, such as CMTA, can help guide your path. Emotional support is just as important as medical information when making decisions about reproduction. While steps may be taken to reduce the risk of passing on CMT, there are thousands of other rare genetic conditions that will most likely not be tested for, and all pregnancies carry a risk of de novo mutations for other diseases. Having a child is ultimately a roll of a many-sided dice, you just never know what you’re going to end up with!

Helpful resources may include:

• Genetic counseling
• CMTA Clinical Centers of Excellence
• Fertility specialists familiar with inherited conditions
• If pregnancy poses health risks, another person may carry the pregnancy using your embryos or those from a donor. Surrogacy laws vary greatly between countries and between states in the U.S.
• CMTA support groups and peer networks, such as CMTA’s The Roots program
• CMTA will host a Lunch & Learn Lunch & Learn webinar on pregnancy in CMT in 2026. Please ensure you’re signed up for our emails to receive the registration details.

Empowerment Through Knowledge

There is no one-size-fits-all approach to family planning in CMT. What matters most is that every person or couple has access to accurate information, compassionate support, and the freedom to make informed choices.