Tacrolimus concentrations after renal transplantation in a mother-neonate dyad: Maternal, neonatal and breast milk measurements.

What is known and objective We aim to add to the few reports on tacrolimus concentrations in breast milk and in maternal, umbilical vein and neonatal blood after maternal renal transplantation. Case summary In a 30-year-old pregnant woman, the tacrolimus concentration at delivery was the same in maternal, umbilical vein and neonatal blood. The breast milk/maternal blood tacrolimus ratio ranged from 0.40 to 0.64. What is new and conclusion The maternal and neonatal blood tacrolimus concentrations at birth are equivalent; thus, one must assume that maternal tacrolimus concentrations directly affect the foetus and/or neonate. Tacrolimus is not detectable in the neonate 3 weeks after birth, suggesting that there is minimal transfer through breast milk.