Wearing comfortable and breathable nursing underwear during breastfeeding will not affect milk production, but if the underwear is too tight, it may affect milk secretion or even lead to milk return. Wearing comfortable and breathable underwear during breastfeeding has no effect on milk production. However, if the underwear is too tight, it may affect the blood circulation of the breasts, resulting in the mammary ducts are not smooth, the milk is stagnant, resulting in breast emptying affected, thus leading to the return of milk, and in serious cases, it will also cause local redness, swelling, heat and pain and other inflammatory reactions. Breastfeeding need to choose the right breastfeeding underwear, the material should choose cotton breathable, the size should choose a little loose a little bit. You should also take good care of your breasts during breastfeeding, which will be more conducive to lactation. If you have any other problems during breastfeeding, it is recommended to consult a professional doctor for guidance.