Overview
Definition:
Weight loss in newborns refers to a decrease in body weight following birth
Physiologic weight loss is a normal, expected phenomenon occurring in the first few days of life, typically resolving within 7-10 days
Pathologic weight loss is excessive, prolonged, or associated with signs of illness, indicating an underlying problem that requires investigation and intervention.
Epidemiology:
Physiologic weight loss is universal, affecting nearly all term newborns, with an average loss of 5-7% of birth weight (up to 10% in some cases)
Pathologic weight loss is less common, with an incidence varying depending on the underlying cause, but it is a significant concern for neonatal morbidity and mortality.
Clinical Significance:
Distinguishing between physiologic and pathologic weight loss is crucial for identifying newborns at risk, ensuring adequate nutrition, preventing complications like dehydration and hypernatremia, and guiding timely management of underlying medical conditions
Early recognition and intervention significantly impact long-term outcomes.
Age Considerations
Term Newborns:
Generally lose up to 10% of birth weight
regain birth weight by 10-14 days
Physiologic loss is primarily due to fluid shifts, meconium and urine excretion, and reduced caloric intake
Pathologic loss may be due to poor feeding, malabsorption, increased metabolic demands, or underlying illness.
Preterm Newborns:
May experience greater initial weight loss due to immature physiological functions, increased insensible water loss, and potentially more significant feeding challenges
Pathologic weight loss is a higher concern and requires closer monitoring and prompt intervention.
Post Term Newborns:
Less prone to excessive weight loss
may even continue to gain weight
However, post-maturity can be associated with complications that might indirectly lead to feeding difficulties and weight loss if not managed appropriately.
Clinical Presentation
Symptoms:
Signs of dehydration: decreased urination (less than 6 wet diapers/day after day 3)
Decreased stool output: fewer than 3 stools/day after day 4
Lethargy or increased irritability
Poor feeding or weak suck
Dry mucous membranes
Sunken fontanelle
Jaundice
Fever or hypothermia
Poor Apgar scores (in severe cases).
Signs:
Decreased skin turgor
Delayed capillary refill
Bradycardia or tachycardia
Hypotension
Oliguria or anuria
Poor muscle tone
Emaciation
Signs of underlying pathology may include abdominal distension, vomiting, diarrhea, respiratory distress, or specific dysmorphic features.
Diagnostic Criteria:
No absolute diagnostic criteria for physiologic weight loss exist beyond exceeding the expected percentage (typically >10% for term infants) or failure to regain birth weight by 14-21 days
Pathologic weight loss is suspected with any of the aforementioned symptoms/signs, especially when persistent or severe.
Diagnostic Approach
History Taking:
Detailed feeding history: frequency, duration, volume, maternal feeding technique (breastfeeding latch, formula preparation)
Maternal health and stress factors
Gestational age at birth
Birth complications
Any recent illness or fever in infant or mother
Medications used by mother or infant
Family history of feeding difficulties or malabsorption syndromes
Bowel movement and urine output pattern.
Physical Examination:
Full physical examination focusing on hydration status: mucous membranes, skin turgor, fontanelle tension, capillary refill time
Assess for dysmorphic features
Evaluate for abdominal abnormalities (distension, tenderness, masses)
Assess for signs of infection or congenital anomalies
Monitor vital signs meticulously.
Investigations:
Routine investigations are not typically needed for uncomplicated physiologic weight loss
For suspected pathologic weight loss: Complete blood count (CBC) to assess for anemia or infection
Electrolytes (sodium, potassium, chloride, bicarbonate) to assess for dehydration and electrolyte imbalances
Blood urea nitrogen (BUN) and creatinine to assess renal function
Blood glucose to rule out hypoglycemia
Liver function tests (LFTs) if jaundice is present
Urinalysis and urine culture to rule out urinary tract infection
Stool analysis for infection or malabsorption if diarrhea is prominent
Consider abdominal ultrasound if obstruction or malformation is suspected
Genetic testing or metabolic screening if specific syndromes are suspected.
Differential Diagnosis:
Inadequate caloric intake: poor latch, insufficient milk supply, incorrect formula preparation, neurological impairment
Increased caloric expenditure: fever, infection, respiratory distress, hyperthyroidism
Poor absorption: congenital malabsorption syndromes (e.g., cystic fibrosis, celiac disease), short bowel syndrome, intestinal dysmotility
Gastrointestinal anomalies: pyloric stenosis, intestinal obstruction, malrotation with volvulus, necrotizing enterocolitis
Metabolic disorders: inborn errors of metabolism
Endocrine disorders: congenital adrenal hyperplasia, diabetes mellitus
Chronic illness: congenital heart disease, chronic renal disease
Environmental factors: insufficient thermoregulation.
Management
Initial Management:
For suspected physiologic weight loss: Ensure adequate hydration and nutrition
Encourage frequent feeds (every 2-3 hours)
For breastfeeding infants: Assess latch and provide lactation support
For formula-fed infants: Ensure correct preparation and adequate volume
Monitor weight daily
For suspected pathologic weight loss: Promptly assess hydration and vital signs
Initiate intravenous fluids if signs of severe dehydration or hemodynamic instability are present
Address any immediate life-threatening conditions such as sepsis or obstruction.
Nutritional Support:
Adequate caloric intake is paramount
Breastfeeding: frequent, effective latch
Supplementation may be needed
Formula feeding: increase volume or frequency
Consider high-calorie formulas or fortifiers
Nasogastric or orogastric tube feeding if oral intake is insufficient or impossible
Parenteral nutrition may be required in severe cases or if gastrointestinal tract needs to be bypassed
Aim for a daily weight gain of 15-30 grams per day once initial loss is corrected.
Medical Management:
Treatment is directed at the underlying cause of pathologic weight loss
Antibiotics for infections
Surgical correction for congenital anomalies
Hormonal replacement for endocrine disorders
Specific management for metabolic disorders
Supportive care includes maintaining thermoregulation, oxygenation, and cardiovascular stability
Regular monitoring of weight, intake, output, and vital signs is essential.
Supportive Care:
Continuous cardiorespiratory monitoring
Strict intake and output charting
Daily weights
Skin care to prevent breakdown
Pain management if indicated
Parent education and support regarding feeding techniques and signs of concern
Multidisciplinary team approach involving neonatologists, pediatricians, dietitians, lactation consultants, and social workers.
Complications
Early Complications:
Dehydration, electrolyte imbalances (hyponatremia, hypernatremia, hypoglycemia, hypocalcemia), hyperbilirubinemia, hypothermia, increased risk of infection, poor neurological development if severe or prolonged hypoglycemia, aspiration pneumonia.
Late Complications:
Failure to thrive (FTT), developmental delays, chronic feeding difficulties, malnutrition-related organ damage, failure to regain birth weight by expected timelines can lead to prolonged hospitalization and increased healthcare costs.
Prevention Strategies:
Early identification of feeding difficulties
Proactive lactation support for breastfeeding mothers
Education of parents on proper formula preparation and feeding cues
Close monitoring of weight gain and hydration in the neonatal period, especially for high-risk infants
Prompt investigation and management of any illness that may impact feeding or metabolism.
Prognosis
Factors Affecting Prognosis:
The underlying cause of pathologic weight loss is the primary determinant of prognosis
Gestational age, severity of illness, presence of comorbidities, timeliness of diagnosis, and effectiveness of management all play significant roles
Infants with correctable issues and good nutritional support generally have a good prognosis.
Outcomes:
With appropriate management, most newborns with physiologic weight loss regain birth weight within 7-14 days
For those with pathologic weight loss, successful treatment of the underlying condition and adequate nutritional support usually leads to catch-up growth and resolution of symptoms
Long-term outcomes depend on the severity and nature of the underlying pathology.
Follow Up:
Infants with significant weight loss or identified pathologic causes require close follow-up by a pediatrician or neonatologist
This may include regular weight checks, nutritional assessments, and monitoring for developmental milestones
Duration and frequency of follow-up are tailored to the individual infant's needs and the underlying condition.
Key Points
Exam Focus:
Differentiate physiologic (expected, self-limiting) vs
pathologic (excessive, concerning) weight loss
Understand the typical percentage of weight loss and regain timelines for term infants
Recognize signs of dehydration and electrolyte imbalance
Key differential diagnoses include inadequate intake, increased losses, and malabsorption.
Clinical Pearls:
Always assess hydration status in any infant with weight loss
For breastfeeding mothers, observe the latch and feeding effectiveness
Documenting feeding volumes, output (urine/stool), and daily weights is critical
Consider asking mothers about perineal tear healing for a clue about fluid intake in the first 24 hours post-partum
The 10% rule: >10% loss or failure to regain birth weight by 14-21 days warrants investigation.
Common Mistakes:
Attributing all weight loss to normal physiologic processes without adequate assessment
Delaying investigation of excessive or prolonged weight loss
Inadequate nutritional support or incorrect fluid management
Failing to consider serious underlying pathologies like sepsis or congenital anomalies
Insufficient follow-up for infants who have experienced significant weight loss.