The primary purpose of sucking is feeding. When babies are sucking and swallowing breast milk or formula, they are gaining needed calories for growth and development. Sometimes, though, infants suck for non-nutritive purposes, using the breast or a pacifier simply for comfort. Learn more about why and when babies might use nutritive or non-nutritive sucking.
The Sucking Reflex
Rooting and sucking are primal reflexes. Fetuses practice sucking in the womb by swallowing amniotic. You can stimulate the instinctive process of feeding by touching the roof of a baby’s mouth. For both breastfeeding and bottle-feeding, this happens when the nipple of the breast or bottle enters the baby’s mouth. Pressure from the nipple on the roof of the mouth prompts the baby’s sucking action. Sucking, along with simultaneous movements of the tongue, draws out the milk. Swallowing begins when a force of fluid reaches the back of the throat. As the baby swallows, the part of the throat connected to the nasal passages closes off. This process briefly suppresses the baby’s breathing, an action that helps the baby drink without choking on the milk.
Sucking and Breastfeeding
When a baby latches on to the breast and begins to suck, this prompts a milk ejection (let-down reflex) from the milk ducts in the breasts. This action makes a sufficient amount of breast milk available in the area just under the areola. As the baby sucks and moves their tongue from the areola to the nipple, the breastmilk drains out through the nipple. Each suck is followed by a swallow. This pattern repeats quickly and continuously as long as milk is immediately available and the baby is hungry—about one suck per second. We call this “nutritive sucking.” There is high milk flow during this period of frequent swallowing. You’ll see the baby’s jaw moving as they swallow the milk. They may start out sucking quickly and then move toward a slower sucking-swallowing pattern as they get to the hindmilk (the higher fat content milk that comes at the end of a feeding). With bottle-feeding, the baby does a similar sucking action with the nipple of the bottle.
Comfort Nursing
Non-nutritive sucking, also called comfort nursing, is when a baby is going through the motions of nursing but not drinking milk. Alternatively, babies may use a pacifier or their fingers for this type of sucking. Generally, babies seek non-nutritive sucking for relaxation and comfort. It often helps them fall asleep. When they are distressed or uncomfortable, non-nutritive sucking often provides relief. Non-nutritive sucking may occur in a few different instances:
At the end of a feedingBetween nutritive sucksWhen the baby is at the breast and the lactiferous sinuses (the spaces inside the breast near the nipple that hold milk) aren’t full
With non-nutritive sucking, the pattern does not repeat quickly and continuously, but rather slowly and with longer periods of rest. Small amounts of milk may be entering the baby’s mouth. During this period, the baby needs many sucks to collect an adequate amount of milk to activate a swallow.
Flow Rate
Another important variable is flow rate, or how quickly milk comes out. This affects how fast the baby will suck and swallow. The quicker the milk flows, the faster the baby will suck and swallow. In bottle feeding, flow rates are generally very consistent; in breastfeeding, they are extremely inconsistent. Before and between milk ejections, and at the end of feedings, the flow rate is very low, which is when non-nutritive sucking occurs. However, during the first and subsequent milk ejections, the flow rates are very high—this is when nutritive sucking happens. So, babies who are breastfeeding will typically experience both nutritive and non-nutritive sucking, sometimes in the same nursing session.
A Word From Verywell
Nutritive sucking nourishes, while non-nutritive sucking provides comfort. If you are breastfeeding, you can choose whether or not and how much to allow your baby to comfort nurse. A pacifier or their fingers can also offer similar relaxation. However, don’t let your baby suck on an empty bottle, as this can introduce excess air into the baby’s tummy. If you have any questions about your baby’s sucking, their fussy periods, their sleep, or their feeding, consult a healthcare provider.
