The main reasons for the sudden decrease in milk secretion during menstruation include: 1. Unreasonable dietary intake: too little dietary intake or insufficient supply of protein, fat and other nutrients in the diet, which can lead to a significant decrease in milk secretion; 2. Poor rest and excessive fatigue due to the care of the child during the period of menstruation can also lead to a significant decrease in milk secretion; 3, The influence of other factors during menstruation makes the mother’s mood depressed for a long time, which leads to the change of endocrine function, thus causing the decrease of milk secretion; 4, the mother can’t breastfeed her child on time, or when the child is breastfeeding, she can’t suck out the milk in the breast, and doesn’t squeeze out the milk in time, which leads to the decrease of reflexive breast milk secretion.