What is the normal total fluid intake (TFI) in infants and how many milliliters (ml) per feed is recommended?

Normal Total Fluid Intake (TFI) in Infants

For term infants in stable growth phase (after the first 2 weeks of life), normal TFI is 140-170 ml/kg/day, while preterm infants require 140-160 ml/kg/day. 1, 2

Phase-Based Fluid Requirements

Fluid needs vary dramatically based on postnatal age and must be understood in three distinct phases:

Phase I: First 5 Days of Life (Adaptation Phase)

Term neonates:

• Day 1: 40-60 ml/kg/day
• Day 2: 50-70 ml/kg/day
• Day 3: 60-80 ml/kg/day
• Day 4: 60-100 ml/kg/day
• Day 5: 100-140 ml/kg/day 1, 2

Preterm neonates >1500g:

• Day 1: 60-80 ml/kg/day
• Day 5: 140-160 ml/kg/day 1, 2

Preterm neonates 1000-1500g:

• Day 1: 70-90 ml/kg/day
• Day 5: 160-180 ml/kg/day 1, 2

Preterm neonates <1000g:

• Day 1: 80-100 ml/kg/day
• Day 5: 160-180 ml/kg/day 1, 2

Phase II: Days 5-10 (Intermediate Phase - Regaining Birth Weight)

• Term infants: 140-170 ml/kg/day 1, 2
• Preterm infants: 140-160 ml/kg/day 1, 2

Birth weight should typically be regained by 7-10 days of life. 1, 2

Phase III: After Day 10 (Stable Growth Phase)

• Term infants: 140-160 ml/kg/day 1, 2
• Preterm infants: 140-160 ml/kg/day 1, 2

Volume Per Feed

The volume per individual feed depends on feeding frequency:

• For term infants feeding every 3 hours (8 feeds/day): Each feed would be approximately 17-21 ml/kg per feed (based on 140-170 ml/kg/day total) 1
• For a 4 kg term infant: This translates to approximately 70-85 ml per feed
• For preterm infants: Feeds are typically more frequent (every 2-3 hours), resulting in smaller volumes per feed of 12-20 ml/kg per feed 1, 2

Critical Considerations and Pitfalls

Environmental factors significantly modify fluid requirements:

• Phototherapy increases needs by 10-20% 1, 2
• Mechanical ventilation with humidified gases reduces needs by 10-20% 1
• Radiant warmers and single-wall incubators increase insensible water losses 2

Excessive fluid administration carries serious risks:

• Patent ductus arteriosus with congestive heart failure 2, 3
• Necrotizing enterocolitis 2, 3
• Bronchopulmonary dysplasia 2, 4

The evidence strongly supports that fluid restriction to meet estimated requirements (rather than liberal fluid administration) reduces mortality and morbidity in premature infants. 3, 4 One landmark study showed that limiting fluids reduced patent ductus arteriosus from 41% to 11% and congestive heart failure from 13% to 2%. 3

Inadequate fluid administration risks:

• Dehydration with weight loss >10% in term infants or >7-10% in preterm infants 1, 2
• Electrolyte disturbances, particularly hypernatremia 2, 5

Monitoring parameters are essential:

• Daily weights to track fluid status 2
• Urine output should remain >1 ml/kg/hour 2
• Serum electrolytes, particularly sodium (target 135-145 mmol/L) 1, 5
• Clinical assessment for signs of dehydration (sunken fontanelle, decreased skin turgor) or fluid overload 6