1 Department of Pediatrics, Hokkaido University School of Medicine, Sapporo, Japan
The frequency of sex chromatin-positive nuclei during the first 7 days of life was determined in oral mucosa smears stained with lactic acetic orcein in three groups of newborn female infants: 28 cases of full-term newborns, 17 cases of infants with low birth weight (less than 2,000 gm) and high gestational age (more than 32 weeks), and 11 cases of infants with low birth weight and low gestational age (32 weeks or less). A transient suppression of sex chromatin frequency was observed for the first 3 days of life in the full-term females, as has been reported by previous workers. The infants with low birth weight and high gestational age likewise showed transient suppression. The infants with low birth weight and low gestational age, on the other hand, exhibited no comparable suppression of sex chromatin. The findings suggest that the mechanism responsible for sex chromatin suppression is related to a physiologic process that develops in the last 8 weeks of gestation.
Submitted on November 13, 1967