If a girl got her first period, we would pinch her cheeks and say Mazel Tov.
If a girl got her first period, we would pinch her cheeks and say Congratulations.
Mazel Tov is a Hebrew congratulatory word. It is often said during times of rites of passage, such as at Bar/Bat Mitzvahs or weddings. It is said with intentions of wishing the participant luck and prosperity as well.
A first period is a time of celebration for fertility as well as a rite of passage, marking a significant time in a young girls life. The pinching of the cheeks causes redness to form at the area being irritated, perhaps signifying the blood from the menstruation. I have also heard similar stories of mothers slapping their children in their face. Although traditionally not intended to be threatening or to hurt too much, perhaps this is a customary ritual which warns the young girl that she better be careful not to get pregnant (for the time has come where it may be possible).
*Rites of Passage was first suggested by Arnold Van Gennep in 1909