Development of the human foreskin during the fetal period.

AIMS: Foreskin development begins at twelfth gestational week through a circular invagination of the ectoderm in the glandular periphery that grows ventrally and totally involves the glans around the twentieth gestational week. Studies of foreskin formation chronology and its histological constituents in human fetuses are rare. The objective of this study is to analyze foreskin development during the second trimester of the human fetal period.
METHODS: We studied twelve well-preserved human fetuses between thirteen and nineteen weeks post conception (WPC), according to the foot length criterion. The fetuses' weight ranged from 70 to 340 g and the crown-rump length from 11 to 18.5 cm. Their penises were formalin-fixed, paraffin-embedded and cut into 5 micrometers sections. Hematoxylin and eosin, Van Gieson solution, Gomori trichrome and Weigert staining were used.
RESULTS: The glans was partially covered by the foreskin in the fetus at 13 WPC and almost completely covered by the foreskin in fetuses at 16 WPC and 17 WPC. The complete foreskin was formed only in the fetuses at 18 and 19 WPC, in which the foreskin totally covered the glans. In all the fetuses studied we observed the presence of preputial lamella and a large amount of mesenchymal tissue between the foreskin and glans.
CONCLUSION: The chronology of foreskin formation in the second gestational trimester is well documented in our article. It is a fast process that lasts around five weeks and is coordinated with penile urethra formation.