Abstract
Significant folate deficiency in 14 out of 37 preterm infants of birthweights 2.0 kg or less was found to be reliably and most conveniently diagnosed by abnormal morphological changes in peripheral blood and confirmed by the response to folic acid. Deficiency appeared to be more common in light-for-dates infants including the smaller of twins. Neither the clinical status nor the levels of haemoglobin or erythrocyte folate was a reliable guide to the presence of megaloblastic erythropoiesis in the very young preterm infant. 100-200 microgram folic acid a day, orally or IM, may be required to ensure an optimal haematological response, and this would be appropriate for therapeutic trial if the diagnosis is in doubt. This amount would also replenish tissue folate stores; larger doses are likely to exceed the requirements of small infants.