FcRn plays a key role in active antibody transfer from mother to fetus.
There was no measurable affinity of anti-TNF CZP binding to human FcRn.
Human FcRn-mediated CZP transcytosis was less than the negative-control antibody.
CZP transport was below detection in 5 of 6 human placentas perfused ex vivo.
Our results support the hypothesis that CZP structure limits its transfer through the placenta to the fetus.