Chance of Having a Dwarf Child

What are my chances of having a baby with dwarfism?

We frequently see incoming search queries related to people asking questions such as What are the chances of having a dwarf baby? and Do dwarf parents always have dwarf children? Since there is a lot of interest in this topic, here is our attempt at making this understandable. (A quick reminder: dwarf or little person is the preferred term, not midget).

Autosomal Dominant Disorders

These types of dwarfism only require one parent to pass on the gene (or through a random mutation at conception). Some examples are achondroplasia, pseudoachondroplasia, hypochondroplasia, and SEDc.

Two Average Height Parents (no history of dwarfism)

  • Approximately 1 in 25,000 (0.004%) chance of a child with dominant dwarfism

Average Height parent and Parent with Achondroplasia

  • 50% chance of child without dwarfism
  • 50% chance of child born with Achondroplasia

Two parents with Achondroplasia

  • 25% chance of average height child
  • 50% chance of child born with Achondroplasia (heterozygous Achondroplasia)
  • 25% chance of homozygous Achondroplasia and is not compatible with life

1 Parent has Achondroplasia, 1 Parent has Pseudoachondroplasia

  • 25% chance of child without dwarfism
  • 25% chance of child with Achondroplasia
  • 25% chance of child with Pseudoachondroplasia
  • 25% chance of child with Achondroplasia AND Pseudoachondroplasia

Can two average height parents have two children with Achondroplasia?

Surprisingly, the answer is yes and it’s very rare. We’re not geneticists, but our high-level understanding is that while most mutations for dwarfism occur at conception, it’s possible that a parent can have a mutation in the precursor cells to the sperm and egg. Therefore, a parent can give multiple children a gene that already has the mutation even though the parent themselves does not have Achondroplasia (it’s called germline mosaicism).

Autosomal Recessive Disorders

These types of dwarfism require both parents to pass on the gene in order to be affected. If a person has only one copy of the gene, they are considered a carrier but not affected and can pass the gene onto their child. Some examples are Diastrophic Dysplasia and Cartilage-Hair Hypoplasia.

Two Average Height Parents (no history of dwarfism and not a carrier)

  • Approximately 0% chance of a child with recessive dwarfism

Two Average Height Parents (carriers for Diastrophic Dysplasia)

  • 25% chance of child without dwarfism
  • 50% chance of child is a carrier for Diastrophic Dysplasia
  • 25% chance of child with Diastrophic Dysplasia

Two parents with Diastrophic Dysplasia

  • 100% chance of child with Diastrophic Dysplasia

Average Height (non-carrier) Parent and Parent with Diastrophic Dysplasia

  • 100% chance of child without dwarfism and carrier for Diastrophic Dysplasia

Average Height (carrier) Parent and Parent with Diastrophic Dysplasia

  • 50% chance of child is a carrier for Diastrophic Dysplasia
  • 50% chance of child with Diastrophic Dysplasia

Dwarfism Book

If you would like to learn more about dwarfism, check out the Dwarfism Book by Betty Adelson.

Did we miss a possibility you’re interested in or get something wrong? Please let us know!

Comments 3

  1. We have an elder daughter 26. We have a son 24 with achondroplasia.. Both me Nad wife are normal no history in family. Daughter is normal… What is the prognosis fro daughters off springs if she marries a normal boy..

    1. In cases like yours where your son is the only one with Achondroplasia, he is the dominant carrier of the gene (FGFR3). Like most dominant types of dwarfism, Achondroplasia is a sporadic mutation. Your Average Height daughter’s chances of having a child with any type dwarfism is the same as any one else in the general population.

      As a point of clarification, the term is average height for a person without dwarfism, not “normal”.

  2. Two Average Height Parents (no history of dwarfism and not a carrier)
    Approximately 0% chance of a child with recessive dwarfism

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