The location of the hymen is at the circumference of the vaginal opening, which is located in the middle of the vestibule behind the external urethra, and is covered by a thin mucosal fold called the hymen. The hymen contains connective tissue, blood vessels, and nerve endings. Most hymens have a hole in the center that is round or crescent-shaped, and a few are sieve or umbrella-shaped. The size of the hymenal pore varies widely, with small pores usually not able to pass a finger and may even be atretic, called hymenal atresia. The hymenal atresia prevents vaginal blood from flowing out of the vagina and prevents menstruation from flowing out of the vagina, necessitating a minor surgery. The hymenal hole can be as large as two fingers or even a hymenal defect. The hymen can be torn by sexual intercourse, or ruptured due to other injuries, and is affected by vaginal delivery, which leaves only the hymenal scar after delivery, i.e., after vaginal birth.