A new study published in Pediatric Research is giving clinicians and parents a more precise way to understand some of the most common—and most confusing—symptoms during infancy. Researchers have developed percentile references for crying, regurgitation, stool consistency, and the Cow’s Milk-related Symptom Score, known as CoMiSS™, in infants considered presumed healthy. The work could help distinguish normal developmental variation from patterns that may warrant closer medical assessment, addressing one of the most persistent challenges in early-childhood care.
Infants frequently cry, spit up milk, and produce stools that vary in color, texture, and frequency. Although these features are usually part of normal maturation, they can also resemble symptoms associated with gastrointestinal disorders, feeding difficulties, or cow’s milk allergy. Without reliable reference values, families and healthcare professionals may struggle to determine whether an infant’s behavior falls within an expected range. The new research provides a statistical framework for interpreting these observations in relation to other infants of similar age.
Percentiles are commonly used in medicine to describe how an individual measurement compares with a reference population. A value at the 50th percentile, for example, represents the midpoint of the observed distribution, while a value at the 90th percentile is higher than that recorded in approximately 90 percent of the reference group. Importantly, a high or low percentile is not automatically a sign of disease. Instead, percentiles show where a child’s characteristics sit within a population and must be interpreted alongside growth, feeding, development, and clinical examination.
The study focuses on crying, one of the earliest and most visible signals of infant discomfort. Crying typically changes over the first weeks and months of life, reflecting neurological development, feeding patterns, sleep maturation, and the gradual emergence of more predictable behavioral rhythms. Measuring crying through standardized reporting can help reveal age-related patterns that are difficult to recognize from isolated parental observations. A reference curve may therefore offer reassurance when crying remains within a commonly observed range, while also helping clinicians identify unusually persistent or intense patterns that deserve further discussion.
Regurgitation is examined through the same population-based lens. Spitting up is common because the infant digestive system is still developing, the lower esophageal sphincter is immature, and babies consume liquid meals while spending much of their time lying down. In most cases, uncomplicated regurgitation is different from gastroesophageal reflux disease, which may involve troublesome symptoms or complications. By describing how regurgitation is distributed among presumed healthy infants, the research may reduce the risk of treating normal spit-up as a disorder while supporting more careful evaluation when symptoms are severe, persistent, or accompanied by poor growth or other warning signs.
Stool consistency presents another interpretive problem. Infant stools can range from loose and seedy to thicker or more formed, depending on age, feeding method, and dietary transition. These differences are often normal, yet stool appearance is a frequent source of anxiety and can be incorrectly linked to allergy or illness. A percentile-based description does not replace medical judgment, but it creates a common language for documenting stool patterns. That standardization could improve communication between families and clinicians and make future research more comparable across countries and healthcare systems.
The investigators also included CoMiSS™, a symptom-based tool designed to support the identification of infants who may have symptoms associated with cow’s milk. The score brings together several clinical features rather than relying on a single sign, reflecting the fact that cow’s milk-related symptoms can overlap with ordinary infant behavior. Establishing how CoMiSS™ values appear in presumed healthy infants is especially important because a score can be elevated for reasons unrelated to cow’s milk allergy. The tool is intended to support clinical assessment, not to function as a standalone diagnostic test.
The word “presumed” is central to interpreting the findings. A study population described as presumed healthy is selected to represent infants without known significant disease, but no reference group can eliminate every uncertainty. Symptoms exist on a continuum, and healthy infants may still cry frequently, regurgitate, or have unusual-looking stools. Conversely, an infant with a clinically important condition may not display an extreme value for every measured feature. Percentile charts are therefore best used as a starting point for conversation, not as an automatic trigger for dietary restriction, medication, or diagnostic labeling.
The potential impact is broad because parental concerns about crying, spit-up, and stools are among the most common reasons infants are brought to medical attention. Better reference data could help clinicians provide evidence-based reassurance while avoiding both under-recognition and overdiagnosis. It may also reduce unnecessary elimination diets, which can affect maternal nutrition, breastfeeding, family stress, and infant feeding choices when introduced without professional guidance. The researchers’ work offers a foundation for more consistent assessment, but its practical value will depend on how the percentiles perform across different populations, feeding practices, and healthcare settings.
As infant-care advice increasingly spreads through social media, simple symptoms can quickly become associated with alarming diagnoses or promoted treatments. The new reference approach provides a more measured alternative: compare symptoms with age-appropriate population data, consider the entire clinical picture, and seek professional evaluation when red flags appear. The study does not suggest that every variation is meaningful, nor that every concern can be resolved by a chart. Its significance lies in making normal infant variability more visible—and giving pediatric professionals better tools to explain where that variability ends and further investigation may begin.
Subject of Research: Percentile reference values for crying, regurgitation, stool consistency, and CoMiSS™ in presumed healthy infants
Article Title: Percentiles for crying, regurgitation, stool consistency, and CoMiSS™ in presumed healthy infants
Article References: Huysentruyt, K., Bajerova, K., Salvatore, S. et al. Percentiles for crying, regurgitation, stool consistency, and CoMiSSTM in presumed healthy infants. Pediatr Res (2026). https://doi.org/10.1038/s41390-026-05323-7
Image Credits: AI Generated
DOI: 10.1038/s41390-026-05323-7
Keywords: infants, pediatric research, crying, regurgitation, stool consistency, CoMiSS™, cow’s milk-related symptoms, percentiles, infant health, gastrointestinal symptoms
Tags: clinical interpretation of infant crying and stool patternsCoMiSS™ score in infant symptom evaluationdevelopmental variation in infant feeding behaviorsdifferentiating normal and abnormal infant behaviorsearly childhood care and symptom assessmentestablishing normative data for infant gastrointestinal symptomsinfant behavior assessmentinfant crying and regurgitation reference percentilesinfant symptom percentile chartspediatric gastrointestinal symptom benchmarksstatistical framework for infant symptom evaluationstool consistency in healthy infants
