While all past discussions of human milk feeding in premature infants have related to the use of pooled banked mature milk, the present research has contributed a new perspective to the assessment of the adequacy of human milk to meet the nutritional needs of the premature infant by examining the hypotheses that:​ 1) mothers giving birth pematurely could produce sufficient quantities of milk of a nutrient composition suited to the needs of their premature infants;​ and 2) mother's own early milk would support a better nutritional status in premature infants than pooled banked milk during early postnatal life.

The first phase of the study examined the nutrient composition of milk from mothers giving birth prematurely (26 to 33 weeks of gestation = PT) as compared to milk of term mothers (38 to 40 weeks of gestation = FT). Complete 24-hour expressions of milk were collected serially over the first 29 days of lactation. Total nitrogen (TX), protein N (PN), and non-protein N (NPN) concentrations decreased linearly with time in both FT and PT milk but were significantly higher in PT milk over the time observed. However the relative distribution of TN was similar in PT and FT milk averaging 82% PN, 8% from the NPN components — urea, free amino acids, uric acid, and ammonia — and the remaining 10% from glucosamine and peptides (molecular weight = 3000 to 14000).

The sodium, potassium, chloride, calcium, phosphorus, and magnesium concentrations in milk were similar between groups over the first four weeks off lactation. However, the concentrations of sodium, potassium, chloride and calcium were higher initially than at the end of the fourth week.

The laclose concentration of milk increased by 25% from the first to the end of the fourth week of lactation while the lipid and total energy concentrations increased by 25% from the first to second week and then remained stable in both groups. Although these changes with duration of lactation were similar in both groups, PT compared to FT milk was consistently 20-30% higher in total energy and lipid concentration and, after the first week, approximately 10% lower in lactose.

From the data on the composition of milk from PT mothers it was predicted that premature infants fed their own mothers early milk, could meet the estimated nutrient requirements for protein, energy, sodium, potassium, chloride, and magnesium but not calcium and phosphorus.

In order to support these predictions on the adequacy of PT milk, a clinical study was designed to investigate N and energy balance, growth and protein nutritional status of three groups of infants matched for gestational age and weight and red either PT milk, pooled breast milk (PBM) or SMA infant formula (n=8/group).

Nutrient balances at the end of the first and second postnatal. weeks demonstrated that No and lipid from PT milk was more efficiently absorbed and retained than from PBM or SMA₂₀. Protein intakes from PT milk averaged 3.0 to 3.2 g/kg/day which meet the estimated requirement for premature infants. More importantly the infants fed their own mothers' milk or SMA₂₄ had apparent N retentions that paralleled intrauterine N retention rates (~325 mg/kg/day), while those fed PBM or SMA₂₀ retained only one to two thirds this amount of N. Consequently, the infants fed their own mothers' milk tended to sustain a better protein nutritional status as measured by blood amino acid levels, plasma protein concentrations (especially plasma albumin) and weight gain than the infants red PBM. At the same time, neither BUN nor blood amino acid levels reflected an excess of protein ingestion from PT milk.

Gross energy intakes of the three groups of infants were similar and averaged:​ 107 kcal/kg/day the first week and 135 kcal/kg/day the second week of life. The greatest loss of ingested calories was through fecal lipid loss which was significantly higher in the infants fed sterilized PBM than in the infants fed PT milk or SMA. However, the average metabolizable energy intakes of all groups were within the estimated energy requirements of 75 to 115 kcal/kg/day.

It was concluded that during the first postnatal weeks of life, premature infants' own mothers' milk was a better source of N, energy, sodium, potassium, chloride, and magnesium than pooled mature milk. Because of the high intakes of N and energy, the premature infants were able to maintain a better protein nutritional status if fed their own mothers' milk than if fed PBM or formula based on mature milk composition (SMA₂₀).