The strained, pushing noise many parents hear their newborn make while sleeping is a common experience that often causes worry. This guttural sound is a normal byproduct of a young body adjusting to life outside the womb. The noisy behavior stems from the immaturity of several bodily systems that have not yet learned to work together efficiently. While the sound can be loud, it is usually a developmental stage the infant will outgrow.
Why Newborns Grunt: Normal Digestive and Respiratory Efforts
The most frequent reason for a newborn’s grunting is a challenge with the digestive process, sometimes referred to as infant dyschezia. This is not constipation, as the baby passes soft, normal stool, but rather a coordination problem. The infant has not yet learned to relax the pelvic floor muscles while simultaneously increasing abdominal pressure to push out gas or stool.
When the urge to have a bowel movement occurs, the baby tightens both the abdominal muscles and the anal sphincter at the same time. This conflict requires the baby to strain and push forcefully, often using the diaphragm muscle, which creates the characteristic grunting sound to generate pressure. This struggle can last for several minutes, with the baby turning red from the effort, until the reflex is coordinated and the stool is passed. The grunting is a sign of effort, not pain, and the baby typically resolves this muscle coordination issue within the first few months of life.
Grunting also occurs due to the immaturity of the respiratory system, specifically the small size of the infant’s airways. Newborns are obligate nose-breathers, meaning they prefer to breathe only through their nostrils. Even a small amount of dried mucus, milk residue, or congestion can partially block the nasal passages, forcing the baby to work harder to move air.
The resulting noise is the sound of air moving past these constricted areas. The grunting can also be a mechanism to maintain a sufficient volume of air in the lungs. By partially closing the vocal cords on the exhale, the baby creates positive pressure, which helps keep the small air sacs, or alveoli, from completely collapsing. This process is a common part of adjusting to independent breathing outside the womb.
The Role of Sleep Cycles in Infant Vocalizations
The timing of these noises, particularly the fact that they happen during sleep, is directly linked to the unique structure of an infant’s sleep cycles. Newborns cycle between two main stages: Active Sleep and Quiet Sleep. Infants spend approximately 50% of their sleep time in Active Sleep, which is characterized by a high degree of brain activity and physical movement.
During this stage, the skeletal muscles are not paralyzed. This lack of paralysis allows for involuntary twitches, facial expressions, and vocalizations such as sighs, squeaks, and grunts. As the baby processes digestive movements or transitions in breathing while in this lighter sleep state, the resulting sounds are easily expressed. The short, frequent nature of newborn sleep cycles means they are constantly transitioning into and out of Active Sleep, leading to continuous vocalizations throughout the night.
Red Flags: When Grunting Signals a Problem
While most newborn grunting is normal, a specific type of grunting can signal a serious respiratory problem that requires immediate medical attention. This pathological grunting is a short, consistent, expiratory sound that occurs with every single breath. It is the body’s attempt to keep the air sacs in the lungs open and prevent them from collapsing, which is a sign of respiratory distress.
Parents should look for other accompanying symptoms indicating the baby is struggling to breathe. One clear sign is retractions, where the skin visibly pulls in between or under the ribs, at the collarbone, or the neck with each inhalation. This shows the baby is using accessory muscles to force air into the lungs.
Other red flags include:
- A blue or dusky color change, known as cyanosis, noticeable around the lips, mouth, or on the nail beds. This indicates the baby is not getting enough oxygen.
- A breathing rate consistently higher than 60 breaths per minute.
- The nostrils flaring with each breath.
- If the grunting is accompanied by a fever or significant lethargy.
If any of these signs are present, the baby needs immediate medical evaluation.