Within-pair differences in a-b ridge count asymmetry in monozygotic twins: evidence for a placental proximity effect.
Asymmetry of a-b ridge count, a dermatoglyphic trait in the second interdigital (ID II) palmar area was studied in 314 identical (MZ) twin-pairs of known placental type. Statistically significant differences were observed for the variability of a-b ridge count with respect to placentation. Monochorionic MZ pairs displayed more within-pair variability than dichorionic MZ twins. Within dichorionic pairs, greater variability was observed in MZ twins when pairs with fused placentas were compared with those with separate placentas. A similar pattern of greater variability in dichorionic fused versus dichorionic separate placentas was also found in 121 same sex dizygotic twin-pairs. The pattern of within-pair differences was consistent with a placental proximity effect like that known for the variability in birth weight in twins.
United Genetics, (Phoenix Perinatal Associates), Ariz.
A C
AC
Bogle
T
T
Reed
J A
JA
Norton
D003878:Dermatoglyphics; D005260:Female; D014644:Genetic Variation / Q000235:genetics; D006801:Humans; D008297:Male; D010929:Placentation; D011247:Pregnancy; D012737:Sex Factors; D014430:Twins, Monozygotic / Q000235:genetics*