Infancy may be associated with a risk of micronutrient depletion due to the high demands of rapid growth. This is particularly true when preterm birth occurs, as the period before term exhibits the highest rate of bodily growth across the lifespan. Folate and vitamin B12 are essential in development, and preterm infants may be particularly susceptible to deficiencies. This is the result of a combination of low stores and high requirements for fast growth and rapid red blood cell production in the context of multifactorial anaemia of prematurity. Micronutrient supply, including vitamin B12 and folate, is delivered through nutritional support, in the shape of parenteral nutrition, fortification of human milk of use of artificial formula. Most of this supplementation will be interrupted by the time the infant is getting ready for discharge home. The investigators previously reported high levels of serum folate in preterm infants at the time of discharge home and in early infancy, but there are no contemporary studies investigating the vitamin B12/folate status in this population. The investigators aim to investigate the prevalence of vitamin B12 deficiency in preterm infants at the time of discharge home.

This is an observational, cross-sectional study of infants born preterm (gestational age at birth <37 weeks) and their mothers. The investigators aim to estimate the prevalence of vitamin B12 deficiency (low vitamin B12, high homocysteine and high MMA) under current nutritional guidelines in preterm (born <37 weeks) babies at the time of discharge in preterm infants under current nutritional guidelines.

The investigators will also study whether the risk of deficiency is different in those on an exclusive breast milk diet or in specific gestational age groups (late -34-36 weeks-, moderate -32-33 weeks-, very -28-32 weeks- and extremely -<28 weeks - preterm infants). Folate status will also be analysed. Exploratory outcomes include correlations between calculated intakes and vitamin levels, blood concentrations of other vitamins and cofactors in the same metabolic pathways, content of B vitamins in preterm maternal milk and performance of potential urinary markers of vitamin B12 deficiency in preterm infants.

The trial will take place in a single tertiary-level Neonatal Intensive Care Unit (NICU) and participant families will be recruited while their infant is an inpatient. The project has received Ethical Approval and Informed Consent for mother and baby/ies will be sought before participation.

This trial focuses on the population of preterm-born (<37 weeks of gestation) infants admitted to the Neonatal Unit.

Inclusion Criteria:

• Gestational age at birth <37 weeks.
• Admission to one of the participating units.
• Full enteral milk feeds established by suck/nasogastric tube

Exclusion Criteria:

• Known or suspected chromosomal, genetic or metabolic abnormalities.
• Major congenital malformations
• Any intercurrent condition that precludes implementation of standard feeding protocols and requires specialized formulas or changes in standard vitamin supplementation.
• Any intercurrent condition that will interfere with the interpretation of results (renal impairment and hypothyroidism can lead to elevated tHcy and MMA, for example).

Preterm infants (born <37 weeks of gestation)