Association of ABO phenotypes and body weight in a sample of Brazilian infants

The relationship between body weight and ABO blood types was examined in a sample of infants included in a sample of Brazilian migrant families collected by N.E. Morton 30 years ago. The results, obtained by one-way analyses of variance using SPSS Release 4, indicate: (1) an excess of females (N = 85) over males (N = 56) due almost entirely to an excess of type A and type B females, (2) no significant differences in body weight by ABO blood type among the male infants, (3) differences between type A females and types O and B female infants with type A females significantly heavier (P = .009) than the other phenotypes, and (4) infant daughters, regardless of ABO phenotype, born to type A mothers are significantly heavier than infant daughters born to type B mothers (P = .016). The results are consistent with earlier work of Kircher (1963), Reed (1967), and Clausen and Hakomori (1989), and suggest that selection on the ABO system may act very early in ontogeny and may act on females and not on males. © 1992 Wiley-Liss, Inc.