Constipation in Babies and Toddlers: When Is It Normal, What Causes It, and What Actually Helps

Research-informed explainer — last updated April 12, 2026

Constipation is one of the most common complaints in pediatric practice, accounting for approximately 3–5% of all pediatric office visits — and it is also one of the most frequently misunderstood, with many parents unsure of what normal stooling frequency actually looks like at different ages. The research-based Rome IV criteria, co-developed by experts including Dr. Samuel Nurko, provide clear diagnostic thresholds and distinguish functional constipation — by far the most common type — from the rare organic causes that require additional workup.

This article draws on research from three pediatric specialists. Dr. Samuel Nurko, Professor of Pediatrics at Harvard Medical School and a pediatric gastroenterologist at Boston Children's Hospital, co-authored the Rome Foundation's canonical papers on childhood functional gastrointestinal disorders including functional constipation in neonates and toddlers (1,080 citations, Gastroenterology, 2016), the NASPGHAN/ESPGHAN evaluation and treatment guidelines for functional constipation (1,059 citations), and an earlier foundational review of constipation evaluation and treatment in infants and children (438 citations). Dr. Todd Mahr of Gundersen Health System contributed to the understanding of cow's milk protein allergy testing (168 citations) — an important differential diagnosis in infant constipation. Dr. Ellen Rome of Cleveland Clinic contributed research on avoidant/restrictive food intake disorder (447 citations) and early nutritional interventions (383 citations), informing the dietary and feeding-behavior context for constipation in young children.

What is normal stooling frequency at different ages?

One of the most important things to establish before diagnosing constipation is whether your child's stool frequency is actually abnormal. Normal range is wide and varies significantly by age and feeding method:

• Newborns (breastfed): May stool after every feeding (6–10 times/day) in the first weeks; after about 6 weeks, it is normal to go several days without stooling. Breastfed infants rarely have true constipation.
• Newborns (formula-fed): Typically stool 1–4 times per day; 1–2 times per day by 3–4 months.
• Infants 6–12 months: 1–3 stools per day is typical once solid foods are introduced.
• Toddlers and preschoolers: Most have 1–2 stools per day, but 3 per week to 3 per day is the normal range.

The concern is not frequency alone — stool consistency and the presence of pain or withholding behaviors are more diagnostically meaningful than counting bowel movements.

How doctors diagnose functional constipation: the Rome IV criteria

Nurko co-authored the Rome IV criteria for childhood functional gastrointestinal disorders (1,080 citations, Gastroenterology, 2016), which define functional constipation in infants and toddlers (under 4 years) as the presence of at least 2 of the following for at least 1 month:

• Two or fewer defecations per week
• History of excessive stool retention
• History of painful or hard bowel movements
• History of large-diameter stools
• Presence of a large fecal mass in the rectum

In older infants who are toilet training or already trained: additionally, one episode per week of fecal incontinence (soiling), or history of large diameter stools that may obstruct the toilet.

The NASPGHAN/ESPGHAN treatment guidelines that Nurko contributed to (1,059 citations) also classify diagnostic alarm features — called "red flags" — that should prompt investigation for organic causes rather than presumptive treatment of functional constipation:

• Delayed passage of meconium (more than 48 hours after birth)
• Constipation from the first month of life
• Failure to thrive
• Bilious vomiting
• Abdominal distension
• Blood in stool without fissures
• Abnormal thyroid, neurological, or spine findings

These red flags suggest conditions like Hirschsprung disease, hypothyroidism, anorectal malformations, or spinal abnormalities that require specialist evaluation.

What causes constipation in babies and toddlers?

Functional constipation (the vast majority)

Functional constipation has no identifiable organic cause — it results from the interplay of diet, habits, and voluntary withholding behavior.

Diet: Formula changes (switching brands or types), the transition to cow's milk at 12 months, low fiber intake, inadequate fluid intake, and excessive dairy consumption are common contributors. Rome's research on early nutritional interventions (383 citations) documents how feeding transitions and dietary composition affect GI function.

Toilet training: The most common trigger for new-onset functional constipation in toddlers. A painful stool during early toilet training leads to voluntary withholding, which leads to harder, larger stools, which leads to more pain — a self-perpetuating cycle that can persist for months or years without intervention.

Voluntary withholding: Children who withhold stool (crossing legs, walking on tiptoes, stiffening) are often misidentified as straining. The telltale difference: withholding behavior involves tightening muscles to prevent a stool from passing, while true straining involves pushing. Recognizing withholding is key to treatment because education and behavior modification are part of the solution.

Cow's milk protein allergy (CMPA)

An underrecognized but important cause of constipation in infants: cow's milk protein allergy. Unlike classic IgE-mediated dairy allergy, CMPA-related constipation is typically a non-IgE cell-mediated response that does not cause immediate hives or anaphylaxis — making it harder to identify. It is more common in formula-fed infants but can occur in breastfed infants if the mother consumes dairy.

Mahr's research on allergen-specific IgE testing in childhood (168 citations) clarifies the diagnostic approach: standard skin testing and blood IgE tests are designed for IgE-mediated allergy and may be negative in CMPA-related constipation. The most reliable diagnostic test is a 2–4 week trial of eliminating cow's milk protein from the infant's formula (switching to extensively hydrolyzed or amino acid-based formula) or from the breastfeeding mother's diet.

What actually works: the treatment evidence

Disimpaction first (if impacted)

Children with chronic constipation often develop fecal impaction — a large, hard mass of stool in the rectum that may cause liquid stool to leak around it (encopresis or soiling). Nurko's guidelines (1,059 citations) recommend disimpaction before starting maintenance therapy, using:

• Oral polyethylene glycol (PEG/MiraLax): High-dose PEG (1–1.5 g/kg/day for 3–6 days) is the most evidence-supported disimpaction method, avoids rectal intervention, and is well-tolerated by children.
• Rectal enemas: Sodium phosphate or mineral oil enemas are an alternative when rapid relief is needed, but are more uncomfortable for children and require caregiver training.

Maintenance laxative therapy

After disimpaction (or for mild-to-moderate functional constipation without impaction), maintenance laxative therapy is recommended until stool pattern normalizes — often for months:

Osmotic laxatives:

• Polyethylene glycol (PEG): First-line maintenance therapy based on the highest evidence. Multiple RCTs demonstrate superior efficacy and tolerability over lactulose. FDA-approved for children as young as 6 months (MiraLax). Dose: 0.4–0.8 g/kg/day, adjusted to produce 1–2 soft stools per day. Mixes invisibly in water or juice.
• Lactulose: Effective alternative; often used in infants under 6 months. Causes gas and bloating in some children.

Stimulant laxatives (senna, bisacodyl): Second-line; appropriate when osmotic agents alone are insufficient. Senna syrup is appropriate for older infants and toddlers.

Dietary interventions

Increasing fluid intake and dietary fiber supports treatment but is insufficient as sole therapy for established constipation. Prune juice and other juices high in sorbitol have a mild laxative effect and can be a useful addition for infants over 4 months. Pureed fruits (prunes, pears, peaches) are appropriate fiber sources when solids are introduced.

Behavioral interventions for toddlers

For toddlers with voluntary withholding and toilet-training-related constipation, behavioral strategies are essential:

• Scheduled toileting: Sitting on the toilet for 5–10 minutes after meals takes advantage of the gastrocolic reflex; use a footstool for appropriate posture
• Reward systems: Sticker charts for sitting on the toilet (not for producing a stool) reduce performance anxiety
• Avoiding power struggles: Constipation that becomes a control issue between parent and child is harder to treat; framing as a physical health problem rather than a behavioral one helps

When to see a specialist

Most functional constipation resolves with the primary care approach above. Referral to a pediatric gastroenterologist is appropriate when:

• Red flag symptoms are present
• Constipation has not responded to 3–6 months of appropriate laxative therapy
• Significant encopresis (soiling) is affecting school and social function
• The clinician suspects underlying motility disorder, Hirschsprung disease, or cow's milk protein allergy requiring dietary management

Questions to ask your doctor

• Does my baby's stooling frequency actually meet the criteria for constipation, or is this within the normal range for their age and feeding type?
• Could cow's milk protein allergy be contributing, and how would we test for that in my infant?
• My toddler is clearly withholding — what behavioral strategies should we be using alongside the laxative?
• How long should we expect to continue the maintenance laxative? Is it safe for months?
• What signs tell me the constipation is fully resolved and it is safe to try stopping the medication?
• Are there any red flag symptoms I should watch for that would indicate this is not functional constipation?

The bottom line

Functional constipation in infants and toddlers is almost always benign and treatable, but requires a systematic approach: rule out organic causes using Rome IV red flags, treat any fecal impaction before starting maintenance therapy, use PEG-based osmotic laxatives as the first-line evidence-based maintenance treatment, and pair medication with appropriate dietary and behavioral strategies. For infants with constipation from the first weeks of life or those who do not respond to initial treatment, a pediatric gastroenterologist can rule out cow's milk protein allergy and less common motility disorders that require targeted management.