2. Congenital absence of a limb or limbs.
Usually the associated shoulder girdle or, less commonly, the associated pelvic girdle is also hypoplastic. A small soft-tissue protuberance may be present at the site of the missing limb.
Amelia is an extremely rare anomaly now. Between 1958 and 1963, it occurred with some frequency as a result of thalidomide embryopathy.
Analysis of the thalidomide anomalies showed that the drug produced limb defects only when taken between the 35th and 45th days after the last menstrual period.
Exposure during the early part of the vulnerable period led to very severe arm defects; such as, amelia or one-finger phocomelia; later exposure led to three-finger phocomelias and femoral and tibial defects.
Exposure near the end of the seventh week resulted only in minor thumb deformities (triphalangia). Exposure after fifty days of postmenstruation was associated with few or no fetal abnormalities.