Do not use the sandwich technique in the following situations.
1) If you have inverted nipples
Occasionally latching problems can be caused by the mother having inverted nipples. In this case, the sandwich technique is unlikely to help the baby latch.
Some mothers have a partially inverted nipple caused by a thick cord running from deep in the breast to the nipple. When using the sandwich technique, the fingers and thumb will press on the cord, making it even tighter and the baby will have even more trouble latching.
To understand the effect of the sandwich technique on an inverted nipple, do the pinch test with and without using the sandwich technique. The results of the pinch test with the sandwich technique should show that the nipple root is softer, more stretchy, and needs less pressure to hold. Do not use the sandwich technique if the nipple moves back into the breast or the nipple root is firmer, less stretchy, or harder to grab using the pinch test.
If the nipple moves inward when using the sandwich technique, avoid it and simply hold the breast as lightly as possible when latching the baby.
2) If you develop a plugged duct
Milk ducts are easily compressed, so you may think the sandwich technique would cause plugged ducts (Geddes 2007). Interestingly, we have found that this is rarely a problem. If you do develop a plugged duct, you should address it and avoid the sandwich technique.
3) If the sandwich does not help
The sandwich technique is most helpful if the breast or areola is firm. As the baby grows, the breast becomes softer and the areola becomes stretchier, eliminating the benefit of the sandwich technique.