Neonatal B-Cell Levels and Infant Health in Newborns Potentially Exposed to Anti-CD20 Monoclonal Antibodies During Pregnancy or Lactation.

Objectives: To report CD19⁺ B-cell counts and possible adverse effects on infants of mothers exposed to anti-CD20 mAbs ≤6 months before/during pregnancy or lactation.

Methods: We conducted a retrospective study using data from the German nationwide neuroimmunologic pregnancy registry. Inclusion criteria involved infants whose mothers received anti-CD20 mAbs ≤6 months before/during pregnancy or lactation, with ≥1 postnatal CD19⁺ B-cell count. Main outcomes were absolute and relative CD19⁺ B-cell counts. Comparison with reference values was performed conservatively in a subgroup with maternal exposure ≤3 months before/during pregnancy. Additional outcomes included pregnancy results, severe infections, and lymphocyte counts.

Results: The cohort comprised 49 infants (F:M 25:24) exposed to anti-CD20 mAbs ≤6 months before/during pregnancy or lactation. CD19⁺ B-cell and lymphocyte counts in 40 infants with maternal exposure ≤3 months before/during pregnancy were comparable with normative values. Only 2 cases of complete CD19⁺ B-cell depletion occurred after second-trimester and third-trimester ocrelizumab exposure, with repopulation observed within 2 months. Exclusive lactation exposure had no significant effect on infants' absolute CD19⁺ B-cell counts.

Discussion: Administering anti-CD20 mAbs before or at the pregnancy onset, or during lactation, seems safe without significant impact on infant B-cell development. However, second-trimester or third-trimester exposure can cause CD19⁺ B-cell depletion due to placental transfer, necessitating monitoring and postponing live vaccines.