Sample Collection
Breast milk, breast milk
An aliquot of 5 mL breast milk was collected twice weekly (Tuesdays and Fridays) after enrollment. Breast milk was heated to 40 °C and gently shaken to homogenize in preparation for feeding the premature infants, then aliquots were taken and stored at −30 °C until further measurement. The time of day at which the milk was obtained from the mother was not taken into account, since the choline content of breast milk (water and fat soluble) does not vary systematically in this respect [