Case report: Evidence for transplacental transfer of maternally administered infliximab to the newborn

Background & Aims: Control of Crohn's disease (CD) is important for conception and sustaining a pregnancy to term. Small series of infliximab use during pregnancy have reported favorable fetal and maternal outcomes. As a result of heightened maternal concern triggered by recent labeling changes, infliximab levels were measured in the newborn of a mother treated with infliximab. Methods: Serum and breast milk infliximab levels were measured by enzyme-linked immunosorbent assay. Results: A 32-year-old woman with treatment-refractory CD continued infliximab therapy throughout pregnancy. Five infusions of infliximab, 10 mg/kg, the last one 2 weeks before delivery, successfully controlled her symptoms. Six weeks after delivery, the breast-fed infant's serum infliximab level was 39.5 mu g/mL. Infliximab was not detected in the breast milk. Serial measurements revealed a continued slow decline of the infant's infliximab levels during the following 6 months, despite resumption of breast-feeding and subsequent retreatments of the mother with infliximab. Conclusions: Clinically significant infliximab levels were detected in the offspring. High infliximab levels in the serum of this infant are likely due to placental transfer, not breast-feeding. Similar to other maternally acquired antibodies, the half-life of infliximab appears prolonged in newborns. The true short-term and long-term implications of exposure to infliximab, during the newborn period are unknown. Patients and physicians must be informed about in utero exposure to infliximab and potentially other therapeutic antibodies. The timing of infusions to minimize antibody transfer to the fetus might be an important strategic consideration when therapeutic antibodies are used in pregnancy.