In an anatomo-pathologic investigation on 21 twins (9 pairs and a set of triplets) who had died within 26 days from birth, the Authors have found a majority of lesions of the respiratory system (in 5 cases hyalin membrane, in 4 bronchpneumonia, in 10 desquamative alveolitis associated with atelectasia, emphysema, congestion, haemorragiae, ouedema and substances ab ingestis). Interval between cotwin death lies between 15-18 hours in 8 pairs, 12 days in one pair, 15-11 hours in the triplet set. The highest frequency of mortality was between the 11th and the 16th day: 55%, which differs from that for single born prematures and immatures. Qualitative and quantitative concordance of lesions was remarkable in seven pairs.

In one pair of twins, who died within 30 hours of each other, only the type of prevailing exsudate differred (leucocytes in one, monocytes in the other), while the degree of the lesions was similar. In another pair of twins, whose death was due to exsudative respiratory lesions, one, dead on the 2nd day, exhibited the symptoms of hyalin membrane syndrome, and the other, dead on the 14th day, the symptoms of bronchpneumonia. The two members of the triplet sets who died first, were affected by an egual degree of desquamative alveolitis, while the third, who died 11 hours later, by a leukocyte bronchial catarrh. With regard to the collected data, the Authors proceed with some considerations.