Double Dominance (Double Heterozygosity) means “having two genes for dominant conditions”. This is pertinent for two people, each having a dominant skeletal dysplasia, as their children will have the possibility of inheriting two genes for skeletal dysplasias, usually resulting in a severe or lethal skeletal dysplasia.
http://medical.lpaonline.org/gen_topics/resourcelist.php?infotype=gentopics&id=18

There are reports of children with double dominance who have lived up to 14 months on a ventilator, although it is not clear if longer survival was possible. (Readers should note that if these children are maintained on respirators, they are unable to experience normal stages of growth and development, i.e., can not be bottle or breast fed but must receive nutrition through a tube, can not roll or crawl, etc)

Achondroplasia is the most common form of dwarfism and those affected have disproportionately short arms and legs. Achondroplasia is inherited as an autosomal dominant trait affecting boys and girls equally. The parents of children with achondroplasia are usually of average height. Achondroplasia is caused by mutation in the fibroblast growth factor receptor-3 gene (FGFR3), and most cases of achondroplasia are due to new mutations that appear for the first time in the affected children.
Achondroplasia can be diagnosed before birth. The limited number of changes in the FGFR3 gene responsible for achondroplasia and the ease with which they can be detected provide the basis for a simple method for prenatal diagnosis.

Pseudoachondroplasia (PSACH) and spondyloepiphyseal dysplasia congenita (SEDC) are autosomal dominant forms of short-limb short stature caused by mutations in genes that encode structural components of the cartilage extracellular matrix. PSACH results from mutations in the cartilage oligomeric matrix protein (COMP) gene, while SEDC is caused by mutations in the gene for type II procollagen (COL2A1).
Am J Med Genet 2001 Nov 22;104(2):140-6

Chorionic villus sampling (CVS) is a procedure for first-trimester prenatal diagnosis. Chorionic villus sampling may be done between the eighth and tenth weeks of pregnancy. The aim is to diagnose severe abnormalities afflicting the fetus. In the procedure, tissue is withdrawn from the villi (vascular fingers) of the chorion, a part of the placenta, and examined.

Visit http://medical.lpaonline.org for more information about forms of dwarfism and complications.