Trisomy 16 in a mid-trimester IVF foetus with multiple abnormalities.

An 18 week foetus with multiple system abnormalities was found to have full trisomy 16. This appears to be only the third reported case surviving into mid-gestation; typically, this common aneuploidy dies post-implantation. Similarities exist in the abnormalities found in the three cases suggesting that there is a 'surviving' trisomy 16 phenotype. It is characterised by: absent hemidiaphragm, pulmonary hypoplasia/aplasia, major cardiac defect, small chest, vertebral and rib defects, cystic kidneys, absent gall bladder, multiple spleens and imperforate anus, together with cleft palate, nuchal webbing/cystic hygroma, microcephaly, marked dysmorphic facial features and dorsiflexed great toe.