Recombinant-type of alfa-L-iduronidase that is used in enzyme replacement therapy in patients with Mucopolysaccharidosis I (MPS I). Its high molecular weight explains the null passage observed in the milk of a nursing mother who had received weekly doses of Laronidase for three months, while she was breastfeeding. No physical or developmental problems in infants in the short or long term were observed. Its low oral bioavailability hampers its passage from the breast milk ingested to the infant's plasma since it is degraded in the gastrointestinal tract due to its proteinaceous nature. It is not absorbed by the gut except in the immediate neonatal period or prematurity when intestinal permeability may be increased. Weekly administration and short half life span allows, if desired, developing strategies to further minimize the risk of exposure (e.g. avoid breastfeeding between 4 and 8 hours after receiving a dose, using the "pump and dump method" of the breast milk while the baby is fed with previously extracted milk)