•Rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone pass the placenta.•R-CHOP during pregnancy might profoundly affect the developing immune system of exposed infants.•B cell lymphopenia, hypogammaglobulinemia and decreased response to vaccination are reported.•Immune monitoring of exposed infants is warranted. The immunomodulating chemotherapeutic drugs rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) have the ablity to pass the placenta during pregnancy and might affect the development of the immune system of exposed infants. In particular rituximab causes a transient and almost complete depletion of CD20 expressing B cells and can remain detectable in the infant several months after birth. In this case series we report on the clinical and immunological outcomes of 3 infants exposed to R-CHOP during pregnancy because of maternal B-cell lymphoma and review other cases that have been published. We show that R-CHOP in pregnancy has a profound effect on the immune system in the first year of life, including B-cell lymphopenia, hypogammaglobinemia, neutropenia and decreased response to immunization. Immune monitoring of exposed infants is warranted.