Objective: To define the sonographic features of spondyloepiphyseal dysplasia congenita (SEDC) and the double heterozygote for SEDC and achondroplasia.
Methods: A retrospective review of 6 pregnancies in one family where one parent has achondroplasia and the other SEDC.
Results: There were 4 double heterozygote pregnancies and 2 where the fetus had SEDC. Shortening of long bones was evident in both conditions from around 16 weeks gestation. Other findings such as an increased nuchal translucency were more variable.
Conclusions: Molecular analysis of the FGFR3 and COL2AI gene once mutations are known in a family such as reported here can inform prenatal diagnosis and help to distinguish between the double heterozygote and a fetus which has inherited a single mutation. The data presented here on the growth of the long bones and other sonographic features associated with SEDC may aid prenatal diagnosis in cases where the mutation is not known.