Participation in sport tends to drop during adolescence, and surveys in many countries show this drop is steeper for girls. The reasons are mostly about experience, not ability.
Common factors reported:
Body image concerns and feeling self-conscious, especially in revealing kit
Periods and puberty-related changes, and a lack of open conversation about them
Feeling less competent or less valued than boys, or teams focused only on the most talented
Changing social priorities and lack of friends in the sport
Practical changes that address these factors: kit choices (for example shorts options or dark colours), private changing spaces, coaches who can talk comfortably about periods, and sessions where friendship and enjoyment come first.
Offering social or less competitive options alongside performance teams gives girls more reasons to stay.
Under-fuelling is worth watching too. Missed or stopped periods are not a normal effect of training and can be a sign of low energy availability, which affects bone and overall health.
Girls and parents should know that this deserves a medical check.