Two extremely preterm infants had silastic lines inserted via the left great saphenous vein for intravenous feeding. Clinical deterioration approximately 10 days later led to lumbar puncture as part of a sepsis screen. Parenteral nutrition solution was recovered in the cerebrospinal fluid and heralded potentially life-threatening catheter malposition. The cases illustrate another percutaneous central line-associated morbidity, which is avoidable by careful verification of line position. All previously reported cases of this unusual complication are reviewed and we describe its likely mechanism. We postulate that the phenomenon is a complication peculiar to percutaneous catheterization of the left lower limb.