What is the risk of intravenous (IV) rituximab (rituximab) on a current pregnancy, given exposure 4 months prior?

Risks of IV Rituximab on Pregnancy with Exposure 4 Months Prior to Conception

Based on current evidence, the risk to the current pregnancy is minimal since rituximab exposure occurred 4 months prior to conception, which is outside the highest risk window for fetal effects.

Rituximab and Pregnancy: Key Considerations

• Rituximab is a chimeric anti-CD20 monoclonal antibody that can cross the placenta, with potential effects on the developing fetal immune system 1
• The manufacturer recommends avoiding pregnancy for 12 months after rituximab exposure due to potential risks 2
• The primary concern with rituximab exposure during pregnancy is B-cell depletion in the newborn, which has been observed primarily with second and third trimester exposure 1

Timing of Exposure and Risk Assessment

• Your exposure occurred 4 months prior to conception, which significantly reduces risk compared to exposure during pregnancy
• The FDA label indicates that rituximab can cause adverse developmental outcomes including B-cell lymphocytopenia in infants exposed in-utero, but your exposure was pre-conception 2
• Most reported cases of neonatal B-cell depletion involve maternal exposure during the second or third trimester 1, 3

Evidence on Pre-Conception Exposure

• Limited data exists on pregnancy outcomes following pre-conception rituximab exposure
• In a case series of women exposed to rituximab, those who received their last infusion before conception (Group C in the study) did not report cases of B-cell depletion in their infants 4
• A review of 231 pregnancies with maternal rituximab exposure found that while some complications occurred, few congenital malformations or neonatal infections were observed 3

Monitoring and Management Recommendations

• While the risk is likely minimal, monitoring of the pregnancy with standard prenatal care is recommended
• If available, consider B-cell count assessment in the newborn after delivery 1
• The American College of Rheumatology guidelines suggest that if a pregnancy is exposed to rituximab, the baby should avoid live vaccines for at least the first 6 months of life 5
• Specifically, for infants with second or third-trimester exposure to rituximab, delaying live attenuated rotavirus vaccine until after 6 months of age is conditionally recommended 5

Breastfeeding Considerations

• According to the FDA label, women should not breastfeed while receiving rituximab and for up to 12 months following the last infusion 2
• Rituximab has been reported to be excreted at low concentrations in human breast milk 2

Risk Comparison with Other Biologics

• TNF inhibitors generally have a better safety profile during pregnancy compared to rituximab, with some (like certolizumab) having minimal placental transfer 6, 7
• If ongoing treatment for your condition is needed during pregnancy, discussing alternative therapies with your healthcare provider would be appropriate

Conclusion

• The 4-month interval between rituximab exposure and conception significantly reduces the risk of adverse effects on the current pregnancy
• While the manufacturer recommends a 12-month interval between rituximab exposure and conception, the available evidence suggests that the actual risk in your case is likely to be low 1, 2, 4
• Standard prenatal care and monitoring should be sufficient, with consideration of B-cell assessment in the newborn after delivery