Explanation

Newborn infants have poor parathormone response to falling calcium levels and this immature physiological response is more marked in preterm infants. Vitamin D nutrition is dependent on maternal supply in utero so infants of vitamin D deficient mothers are likely to suffer from vitamin D deficiency as well and may show signs of rickets - whether preterm or term. Difficulty maintaining calcium requirements in preterm infants, poor calcium absorption and possibly increased calcium loss from the kidneys due to diuretics given to manage fluid overload will contribute to poor bone mineralisation and the clinical features of rickets in the preterm infant. Young infants are prone to convulsions in association with hypocalcaemia.