Let me tell you a secret. There is a small percentage of girls who have no hymen at all or are underdeveloped. However, menstruation comes normally (if there are no other abnormalities or diseases) and on time.
And here's some information from the Internet: The pathology of the hymen includes its congenital absence (aplasia), congenital absence of a hole (imperforated hymen) or its secondary infection (atresia) as a result of cicatricial or adhesions.
The presence or absence of a hymen modern young people in most cases do not attach importance to that decisive confirmation of a girl's chastity, as was customary in former times. However, in some cases, the girl's lack of blood during defloration on the wedding night can cause jealousy in the young spouse and conflicts against the background of his ignorance about the structural features of the female genital organs and their possible individual characteristics
I explain "on the fingers". I must say right away that this is a myth and I will try to explain its origin. The loss of innocence before the arrival of the first menstruation or after them does not affect anything, the beginning of menstruation is only an indicator of the beginning of a girl's "growing up". And for pregnancy, ovulation is necessary. It is not uncommon for the first menstruation to pass without ovulation, which means that the girl will not be able to get pregnant, hence this myth follows. If everything is in order with the body, matured, ovulation will go as it should - then pregnancy is possible.