Overview of the Sucking Reflex in Newborns

Baby smiling to mother during breastfeeding
Kevin Liu / Getty Images

The sucking reflex is probably one of the most important reflexes your newborn has. It is paired with the rooting reflex, in which a newborn searches for a food source. When he finds it, the sucking reflex allows him to suck and swallow the milk. 

Your baby does this without thinking about it because it's an innate instinct that is actually quite soothing to him as well. Some babies do have a little more trouble with it, however. There's a simple way you can test your baby's sucking reflex and things you can do to work through sucking problems.

The Sucking Reflex

The sucking reflex is one of seven natural reflexes newborns have, including the Moro reflex, the grasping reflex, the rooting reflex, the stepping reflex, and the fencing reflex. These are essential to their first few weeks and months of life. As the months pass, they begin to consciously do the actions and become able to control them as they develop.

The sucking reflex is essential for feeding. Babies begin practicing it in the womb and it becomes fully developed by 36 weeks. This is why you may have caught a glimpse of your baby sucking his thumb or hand on the ultrasound. It's kind of like a warm-up exercise for the real world.

While you may think of sucking as a simple process, it actually occurs in two steps. First, the baby holds the nipple between his tongue and the roof of his mouth. Then, he will actually begin to suck by moving the tongue up and down. The action is the "expression" of milk, which supplies the food.

Test the Sucking Reflex

If you touch the roof of your baby’s mouth with your finger, pacifier, or nipple, he will instinctively begin sucking. Around 2 to 3 months of age, this sucking will be a result of conscious effort rather than a reflex. Keep in mind that every time your baby exhibits this reflex, it doesn’t necessarily mean that he’s hungry. Sucking is a soothing and enjoyable activity on its own. Babies also have a hand-to-mouth reflex, where they may suck on fingers or hands. 


Some mothers are slow to start breastfeeding and it may be because you're not triggering the sucking reflex. It’s not just the nipple that needs to go into your baby’s mouth, but a fair amount of your areola as well. If you just have the tip of your nipple in his mouth, it may not be far enough back to stimulate the sucking reflex. Also, the milk sinuses won’t be properly compressed by your baby’s tongue and jaw.

Preemies and Sucking Problems

Premature babies may have a weak or immature sucking ability because the reflex has not fully developed. You may notice a combination of sucking issues, including: 

  • Disorganized or inefficient sucking patterns
  • Impaired tongue shaping or movement
  • Trouble synchronizing the suck and swallow with breathing
  • Weakened lip seal
  • Weakened stability of the inner cheek

The last point is part of a complication that affects preemies known as Infant Respiratory Distress Syndrome (RDS). Babies with RDS have difficulty synchronizing their sucking, swallowing, and breathing. This can have a negative impact on feeding as they can't withstand long feeds and tend to tire easily. As a result, the newborn could be at risk of poor nutrition.

The sucking reflex often develops in premature babies over the first few weeks , even by the time they reach their original due date. Until then, they're fed via feeding tubes. Researchers continue to look at the sucking reflex and its relationship to swallowing and breathing. The hope is to develop possible therapies that can help premature babies better develop this essential skill.

A Word From Verywell

Knowing how the sucking reflex works can help you solve any breastfeeding difficulties you may be having with your baby. Sometimes simple things like a change in position can make a big difference. If you have questions or are concerned that your baby is not getting enough food, contact your doctor. You might even find a lactation consultant helpful.

6 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Reflexes in newborns. Cincinnati Children’s Hospital Medical Center.

  2. Geneva: World Health Organization In: Baby-Friendly Hospital Initiative: Revised, Updated and Expanded for Integrated Care.; 2009. Session 6, How milk gets from breast to baby. 2009.

  3. Greene Z, O'donnell CP, Walshe M. Oral stimulation for promoting oral feeding in preterm infants. Cochrane Database Syst Rev. 2016;9:CD009720.  doi:10.1002/14651858.CD009720.pub2

  4. Respiratory distress syndrome in premature babies. Stanford Children’s Health.

  5. Liu YL, Chen YL, Cheng I, Lin MI, Jow GM, Mu SC. Early oral-motor management on feeding performance in premature neonates. J Formos Med Assoc. 2013;112(3):161-4.  doi:10.1016/j.jfma.2012.08.003

  6. Lau C. Development of Suck and Swallow Mechanisms in Infants. Ann Nutr Metab. 2015;66 Suppl 5:7-14.  doi:10.1159/000381361

Additional Reading

By Stephanie Brown
Stephanie Brown is a parenting writer with experience in the Head Start program and in NAEYC accredited child care centers.