1) How nipple shields can help a baby latch and stay latched
How nipple shields help a baby latch remains uncertain and there are a number of theories.
a) Less strength required to latch
To latch and stay latched, a baby needs to create enough suction to keep a teat, consisting of the nipple and nipple root, deep inside the mouth. Babies with weak suction cannot do this. Nipple shields may compensate for the weak suction by giving the baby a preformed teat to replace the nipple and nipple root (Meier 2000).
b) Less strength required to stay latched
Some babies, especially premature ones, tire easily when breastfeeding. Using a nipple shield seems to require less suction, so these babies can breastfeed longer before tiring out.
Weak babies will let go of the breast more often and frequent re-latching can also tire them. When using a shield, they do not have to come off and recreate the teat to resume breastfeeding but rather can just reapply the vacuum, as the teat is already in place.
c) The nipple shield creates a better teat
Some nipples and nipple roots have barriers to the baby latching, such as a slightly inverted nipple or a firm nipple root. The nipple shield cone gives the baby a better teat.
2) How a nipple shield can help a small, premature baby take in more milk.
The tip of the nipple shield acts as a storage area for a small amount of milk that collects when the baby pauses between sucking periods. This milk is available when sucking starts again and may increase the amount of milk a baby takes in.
3) How nipple shields can reduce nipple pain
The reduced amount of suction and the barrier created between the nipple and the baby’s mouth when using a nipple shield may prevent or reduce the amount of nipple trauma.
Babies with latching problems may clamp on the nipple and cause pain. This can be eliminated if the baby can latch and suck normally by using a nipple shield.
4) How a nipple shield can reduce the rate of milk flow
By letting milk leak out from under the rim, nipple shields can reduce the rate of milk flow.