Mechanisms of twinning. I. Effect of environmental diversity on genetic expression in monozygotic multifetal pregnancies.

OBJECTIVE

To examine, using fingerprint homology, the interaction of genetic and environmental factors in arriving at the final phenotypic expression in uniovular triplets, quadruplets and quintuplets.

STUDY DESIGN

The fingerprints of several multifetal sets were collected and matched. A total of 250 fingers were printed. A comparison based on the classic dactylographic patterns was made. Zygosity of each set was known from placental chorionicity studies, as well as blood typing and physical similarities.

RESULTS

As the monozygotic set size increased, the ipsilateral print concordance diminished. At one extreme, with twins there is 88% homology; at the other end, with quintuplets the correspondence is 71%.

CONCLUSION

The overall trend of these results paralleled increasing intrauterine environmental diversity and tended to support the volar pad pressure hypothesis of prenatal fingerprint development.