Clear and delicately provided information at the right moment is the key to chastity formation:
"Parents are well aware that their children must be treated in a personalized way, according to the personal conditions of their physiological and psychological development, and taking into due consideration the cultural environment of life and the adolescent's daily experience. In order to evaluate properly what they should say to each child, it is very important that parents first of all seek light from the Lord in prayer and that they discuss this together so that their words will be neither too explicit nor too vague. Giving too many details to children is counterproductive. But delaying the first information for too long is imprudent, because every human person has natural curiosity in this regard and, sooner or later, everyone begins to ask themselves questions, especially in cultures where too much can be seen, even in public" (TMHS, 75).
Information presented should be adapted to the child's stage of development, whether they are in the age of innocence, puberty, adolescence, or young adulthood. Direct information about genital sexuality is appropriate in puberty and beyond. In a small child and in the age of innocence, children are curious about pregnancy and the birth of a brother or sister. Simple facts about pregnancy can be presented in light of wonder, awe, and joy at the creative work of God who designed new life to be cared for in the mother's body, near her heart (Cf. TMHS, 76).