21-week pregnancy with trisomy 18 (Edwards syndrome) − bone malformations highlighted
Edwards syndrome, also known as Trisomy 18 (T18) or Trisomy E, is a genetic disorder caused by the presence of all or part of an extra 18th chromosome. Some physical malformations associated with Edwards syndrome include small head (microcephaly) accompanied by a prominent back portion of the head (occiput); low-set, malformed ears; abnormally small jaw (micrognathia); cleft lip/cleft palate; upturned nose; narrow eyelid folds (palpebral fissures); widely spaced eyes (ocular hypertelorism); drooping of the upper eyelids (ptosis); a short breast bone; clenched hands; choroid plexus cysts; underdeveloped thumbs and or nails, absent radius, webbing of the second and third toes; clubfoot; and in males, undescended testicles. The diagnosis of Trisomy 18 is by ultrasound and amniocentesis, the fetal DNA being examined for genetic abnormalities. Therapeutic abortion can be done.