The hymen is a membrane that covers the opening of the vagina at birth but usually perforates spontaneously before puberty. If the initial opening of the hymen is small it may tear, with slight loss of blood, at the first occasion of sexual intercourse.
Hymenotomy is the incision of the hymen. This operation may be carried out on a young girl if the membrane completely closes the vagina and thus impedes the flow of menstrual blood (see menstruation). It is also performed to alleviate dyspareunia (painful intercourse).