Some common physical abnormalities characteristic of Trisomy 18 include:
- low set ears
- small head (microcephaly) that is abnormally shaped
- small jaw (micrognathia)
- small mouth
- clenched fists with overlapping fingers
- congenital heart defects
- kidney defects and problems
- underdeveloped fingernails
- undescended testicle (cryptorchidism) in males
- unusual shaped chest (pectus carinatum)
Some of these abnormalities may be seen on a comprehensive ultrasound. However, ultrasound is not diagnostic of genetic disease. In addition, ultrasound cannot detect all birth defects, especially mental disabilities, such as autism and mental retardation.
We recommend that you and your partner meet with a genetic counselor to discuss the benefits and limitations of your partner's screening test, comprehensive ultrasound, as well as your diagnostic testing options (such as amniocentesis). A genetic counselor can be found at the National Society of Genetic Counselors website or through companies like mine, AccessDNA. More information on Trisomy 18 can also be found at AccessDNA.