Interethnic variability in birth weight and genetic background: a study of placental alkaline phosphatase.

The relationship between human placental alkaline phosphatase (PLAP) genotype and birth weight is investigated in a sample of white, black and Puerto-Rican new-born infants from New Haven, Connecticut (total 710 subjects). Black and Puerto-Rican infants show a higher incidence of growth retardation and a higher frequency of ALPp*1/1 genotype as compared to whites. The proportion of newborns with a low birth weight (below the 10th percentile) is lower in infants with ALPp1/1 genotype than in those with other PLAP genotypes, especially among non-whites. It is argued that the higher frequency of ALPp1 allele among non-whites might be, at least in part, a consequence of their adaptation in the past to environmental conditions adverse to optimal intrauterine development.