Infant reflux: it’s not just spit up

If you’ve ever been told, “It’s just reflux—babies spit up!” and felt like that didn’t quite explain what was happening with your baby, you’re not alone. Reflux in infants can range from mild and harmless to chronic and distressing, and while it’s often dismissed as a normal phase, there are many potential underlying causes worth understanding. As both parents and professionals, it’s helpful to know that reflux isn’t just about an immature digestive system. It can be influenced by everything from tongue ties and feeding techniques to food sensitivities, anatomical differences, and even neurological conditions. This post is a comprehensive, no-stone-unturned list of every possible cause of reflux in infants—so whether you’re supporting families or navigating reflux with your own baby, you’ll walk away with a clearer understanding of what might be going on behind the spit-up.

🔍 Anatomical Causes

These are structural or physical issues that directly impact digestion, swallowing, or how milk/formula moves through the GI tract.

➤ Upper GI/Oral Structures

• Tongue tie (ankyloglossia): Can lead to aerophagia (swallowing air), poor latch, and ineffective milk transfer—exacerbating reflux.

• High palate: Leads to poor seal around the breast or bottle nipple → aerophagia + shallow latch.

• Shallow latch: From oral dysfunction, breast shape, or anatomical restrictions → more air swallowing.

• Micrognathia/retrognathia (small or recessed jaw): Common in conditions like Pierre Robin sequence; causes poor latch and airway obstruction → increases reflux.

• Cleft palate or submucous cleft: Affects suck, swallow, and breathing coordination.

• Laryngomalacia: Floppy laryngeal tissue → inspiratory stridor + reflux-like symptoms from increased negative pressure during breathing.

• Vocal cord paralysis or paresis: Can interfere with swallowing coordination and lead to secondary reflux.

➤ Lower GI Structures

• Immature or weak lower esophageal sphincter (LES): Most common cause of physiologic reflux in infants.

• Hiatal hernia: Stomach pushes through diaphragm → contributes to reflux.

• Pyloric stenosis: Hypertrophy of the pylorus causing forceful vomiting (not reflux per se, but often misdiagnosed as reflux initially).

• Malrotation/volvulus: Abnormal gut rotation can cause obstruction, vomiting, and mimic reflux.

• Tracheoesophageal fistula or esophageal atresia (TEF/EA): Surgical correction may lead to chronic reflux.

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🍼 Feeding-Related Causes

Feeding technique, volume, and tools all play a role.

• Aerophagia (air swallowing): Due to poor latch, fast flow, bottle shape, or feeding position.

• Overfeeding: Exceeds stomach capacity → regurgitation.

• Fast milk let-down (or bottle flow too fast): Leads to gulping and more spit-up.

• Infrequent burping: Allows trapped air to push milk up.

• Feeding position (laid back vs reclined): Lying flat during or after feeds worsens reflux.

• Suboptimal bottle nipple shape: Some designs encourage excess air intake or poor latch.

• Paced bottle feeding not used: Increases risk of overfeeding and aerophagia.

• Feeding while sleepy or distracted: Poor coordination of suck-swallow-breathe → increased reflux risk.

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🧠 Functional & Neurological Causes

These relate to how the body processes food or how the nervous system controls digestion.

• Immature digestive system: Normal in young infants; LES tone improves over time.

• Delayed gastric emptying: Milk sits longer in the stomach → more likely to reflux.

• Dysmotility of the GI tract: Includes conditions like intestinal pseudo-obstruction.

• Neurological impairment (e.g. cerebral palsy, HIE): Poor muscle tone + swallowing dysfunction = higher reflux risk.

• Sensory processing issues: May interfere with coordinated suck-swallow-breathe patterns.

• Vagal nerve dysfunction: Affects esophageal tone and gastric emptying.

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🌾 Allergy and Sensitivity Causes

These can inflame the gut or cause delayed gastric emptying.

• Cow’s milk protein allergy (CMPA) – most common allergy causing reflux-like symptoms.

• Soy protein allergy – often co-occurs with CMPA.

• Food protein-induced allergic proctocolitis (FPIAP) – can coexist with reflux.

• Non-IgE-mediated food sensitivities – harder to detect but can cause chronic gut inflammation.

• IgE-mediated allergies – may cause vomiting shortly after feeding.

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🌬 Respiratory & Environmental Factors

These can mimic reflux or exacerbate it through increased intra-abdominal pressure.

• Chronic nasal congestion or mouth breathing: Affects coordination of suck/swallow/breathe.

• Passive smoke exposure: Increases acid production + lowers LES tone.

• Environmental allergens: May contribute to chronic nasal congestion.

• Excessive crying or colic: Increases air swallowing + abdominal pressure.

• Frequent coughing (from illness, asthma, etc.): Can exacerbate reflux.

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🧬 Medical Conditions / Syndromes

Rare or more severe underlying issues.

• Sandifer syndrome: Arching/spasms due to reflux-related pain; may be mistaken for seizures.

• Eosinophilic esophagitis (EoE): Chronic allergic inflammation of the esophagus.

• Congenital GI anomalies: Like duodenal atresia or annular pancreas.

• Genetic syndromes (e.g. Down syndrome, CHARGE): Often involve hypotonia and poor coordination.

• Inborn errors of metabolism: Can present with vomiting or feeding intolerance.

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💡 Other Contributing Factors

• Medications (maternal or infant): Antibiotics, caffeine, etc., may irritate the gut or cause dysbiosis.

• C-section delivery: May be linked to delayed gut colonization.

• Antibiotic exposure: Disrupts microbiome → possible impact on digestion.

• Maternal diet (in breastfeeding): May influence gut inflammation if allergens pass into milk.

• Stress (infant or maternal): Cortisol affects gut motility and LES tone.

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🧾 Reflux is rarely caused by just one thing. It’s almost always a perfect storm of a few interacting issues—immature anatomy, feeding technique, possibly a little air swallowing, maybe a gut sensitivity, maybe a fast letdown. Some babies just hit the reflux jackpot 🃏.

If you’re seeing significant reflux—especially with weight loss, pain, sleep disruption, or refusal to feed—then it’s time to dig deeper. But if it’s “happy spitting” and baby is growing well, most of the time it’s just their body learning how to do its job.