Which of the following criteria must be met for lactational amenorrhea to be effective?

Lactational amenorrhea, a natural form of contraception, is most effective under specific conditions that enhance the hormonal changes necessary to suppress ovulation. The correct answer highlights that for lactational amenorrhea to be effective, the infant must be under 6 months old and exclusively breastfeeding on demand.

This demand breastfeeding stimulates the production of prolactin, a hormone that not only supports milk production but also inhibits the hormonal cycle that leads to ovulation. Exclusive breastfeeding means that the infant receives no supplementary feeding, which helps to maintain elevated prolactin levels and thus suppresses the return of menstrual cycles. Infants under 6 months are typically more dependent on breastfeeding, making this timeframe crucial for effective lactational amenorrhea.

While the other options may include some beneficial elements of breastfeeding, they do not encompass the critical requirements as accurately as the correct choice. For instance, exclusively breastfeeding every 4 hours can limit the frequency of feeds, potentially reducing the continuous stimulation necessary to inhibit ovulation. The option regarding night feedings focuses on sleep patterns rather than breastfeeding frequency, and while good health of the birthing person is important for overall wellness, it is not a direct criterion for the effectiveness of lactational amenorrhea.