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About

Ensuring proper hydration and caloric intake in the first weeks of life is critical for renal function and growth. Newborns, particularly those with low birth weight or born preterm, have evolving fluid requirements that change daily as their kidneys mature. This calculator utilizes standard pediatric protocols to determine the total daily fluid volume (ml/day) required based on exact weight and postnatal age. It distinguishes between Term and Preterm infants, adjusting coefficients to account for the higher evaporative losses and metabolic needs of premature babies.

Fluid overload can lead to edema or patent ductus arteriosus complications, while dehydration risks hypernatremia. This tool provides a precise volume breakdown, dividing the total requirement into manageable feeding intervals (e.g., every 3 hours) to assist parents and clinicians in planning safe feeding schedules.

pediatrics infant feeding formula calculation fluid requirements baby health

Formulas

The calculation relies on a stepwise escalation of fluid coefficients (C) relative to the infant's weight (W). The total daily volume (V) is derived as:

Vtotal = W × Cage

To determine the volume per feed (Vfeed) based on frequency (f):

Vfeed = Vtotalf

For caloric intake, standard formula or breast milk is approximated at 20 kcal/oz (approx. 0.67 kcal/ml).

Reference Data

Postnatal AgeTerm Fluid Coeff (ml/kg)Preterm Fluid Coeff (ml/kg)Target Calories (kcal/kg)
Day 1 (0-24h)6070 - 8040 - 50
Day 2 (24-48h)8090 - 10060 - 70
Day 3 (48-72h)100110 - 12080 - 90
Day 4 (72-96h)120130 - 140100 - 110
Day 5+150150 - 170110 - 120
Week 2+150 - 180160 - 180120+
Month 1150160110
Month 2140150110
Month 3130140105
Month 6120130100

Frequently Asked Questions

A newborn's kidneys are not fully efficient at concentrating urine immediately after birth. Additionally, the body experiences a physiological weight loss due to extracellular fluid contraction. The gradual increase in fluid intake (e.g., 60ml/kg to 150ml/kg) matches the renal maturation process and prevents fluid overload.
Preterm infants have thinner skin and a larger surface area relative to weight, leading to higher transepidermal water loss. Consequently, their baseline fluid requirements are typically 10-20% higher than term infants to maintain hydration and electrolyte balance.
The tool calculates total fluid volume. While it estimates calories based on standard density (20 kcal/oz), adding fortifiers increases caloric density (e.g., to 24 kcal/oz) without significantly changing the required fluid volume. Always follow specific prescription for fortified feeds.