Sex-chromatin in Iranian newborn females

The incidence of sex-chromatin-positive cells during the first five days of life was investigated in buccal smears stained with aceto-orcein in three groups of newborn females: 51 term infants, 17 small-for-date prematures and 9 prematures with birth weight appropriate for gestational age. In addition, single buccal smears were obtained from a control group of 50 older female children. No significant difference was found in the number of sex-chromatin positive cells between the three groups of infants. The mean incidence of sex-chromatin-positive cells in the neonatal period was lower than that of the older control girls, as has been reported by previous workers. The mean incidence of sex-chromatin-positive cells on the fifth postnatal day never reached 17% which was the mean frequency of sex-chromatin positive cells in older controls. This contrasts with the findings of other workers who reported the rise of sex-chromatin positive cells to occur on the second or third days of life.