[Genetico-statistical analysis of multiple birth factors in man. III. Component analysis of multiple birth factors]

Based on the component analysis of correlation matrices for five indicies (parents' age by the moment of twin birth, the number of proband's pregnancy, the beginning of mother's coitus and menarche) characterizing four specified family groups (MZ and DZ load multiple birth and MZ and DZ sporadic multiple birth) at least 6 independent trends of multiple birth factors influence have been revealed. Gases of burdened and sporadic multiple birth turned out to differ in some of the specific trends. At the same time while cases of MZ and DZ load multiple birth differ in some of the trends, they appear to be much more similar to one another than those of MZ and DZ sporadic multiple birth. The data obtained make it possible to assert that first, according to the mechanism of the appearance, there exist at least four main multiple birth groups, specified above, and second, there are multiple birth factors being both common to all groups and specific to each of them separately. At this some of the defined factors influence mainly as implementing hereditary determined trend to multiple burth, while the others in the absence of predisposing genotype perform apparently as casual. The present study data confirm the concept, formed on the basis of genealogical analysis, that genetical factors involved in the determination of MZ and DZ multiple birth are of definitely common character. In addition to that the results of the study make it possible to conclude that multiple aproach in the statistical analysis of quantitative characteristics (multiple birth factors in the present case) is extremely sensitive and results in non-routine conclusions the effects of which can be directly changed.