Contact between the immune systems of mother and child during pregnancy has an impact on transplantation later in life. Exposure to inherited paternal human leukocyte antigens (HLA) (IPA) and the noninherited maternal HLA antigens (NIMA) can lead to either immunization or tolerization. Exposure to IPA seems to have a more immunizing effect as the mature immune system of a mother can form anti-HLA antibodies against the foreign paternal HLA molecules. On the other hand, exposure of a child to the NIMA antigens during pregnancy may lead to NIMA-specific tolerance. This review provides an overview of the current knowledge on the impact of this fetal-maternal interaction on the alloimmune response and clinical transplantation.