The development of a total of 58 triplets, quadruplets, and quintuplets, born in the province of Danzig in the years 1957-1971, is analysed. The examinations show that the physical development of multiplets in the first year of age is similar to that of singletons, irrespective of their social conditions. In the second year of age, however, multiplets with bad social conditions showed a much worse rate of development.

Only half of the 56 children examined by a psychologist reached IQ norms, the others being on the verge of normalcy and mental deficiency, or even lower. Out of 30 school-age children, 16 had difficulties in learning and 15 of these showed features of mental development deficiency.