Only about 1 in every 20 boys is born with a retractable foreskin. This reflects the fact that the histologic (tissue) development of the foreskin is usually not complete at birth.
The foreskin is thus not fully separable from the glans in about 96% of newborn boys. By a year of 1 year, the foreskin can be retracted in 50% of boys and by 3 years, the foreskin can be retracted in 80% to 90% of uncircumcised boys.
Newborn circumcision diminishes the risk for cancer of the penis and lowers the risk for cancer of the cervix in sexual partners. It also decreases the risk of urinary tract infections and lowers the risk of sexually transmitted diseases, including especially HIV.