Twin zygosity and placentation

Abstract

The relationship between placentation and zygosity is discussed in an unselected series of 326 twin births. Zygosity determinations were based on sex, red‐cell antigens ABO, MNSs, Rh, Lua, K and Fa, the red‐cell enzymes Ac. P., 6‐PGD, PGM1 and AK and placental alkaline phosphatase. The results indicate that, whereas dizygotic twins are always dichorionic, between 15% and 20% of monozygotic twins may also be dichorionic. Tables are given which allow information on the enzyme phenotypes to be utilized in estimating the probability of dizygosity in the case of twin pairs alike for all characters tested, where the types of the parents are unknown. Copyright © 1968, Wiley Blackwell. All rights reserved