Is my baby at risk for birth defects?

Here is My Question:
My last infusion of Rituxan was Dec 17th. I just found out I'm pregnant Feb 11th. I'm currently 6 weeks. I'm worried that the medicine will effect my baby. I have emailed my doctor but I haven't got a response. Can you please tell me if my baby is at risk of birth defects? 

Answer:
Reports of pregnancy outcomes after maternal exposure to rituximab generally report excellent outcomes. Many of the woman exposed to rituximab prior to or during pregnancy were also exposed to chemotherapies known to be potentially harmful to a fetus, so this is good news. There is no evidence yet of any major birth defects.

Rituximab is present in your blood for up to 3 months and eliminates B cells expressing CD20 from your blood stream for a variable period of time depending on the dose you received. If you received the standard dosing regimen for MS, you can expect rituximab to lower your B cell count for more than 6 months.

Rituximab is an IgG1 class monoclonal antibody and is able to cross the placenta and enter the fetal blood circulation. This ability of IgG antibodies to cross the placenta is time dependent with very little IgG antibody crossing in the first trimester, more in the second trimester and the maximum occurring in the third trimester just prior to birth. As a result, maternal treatment with rituximab prior to or very early in pregnancy often results in less fetal exposure to the drug.

The most common abnormality noted in children born to mother’s exposed to Rituximab is a temporary lowering of blood cell counts. This can exclusively affect white blood cell counts or also include platelets or red blood cell counts. These low counts tend to recover quickly after birth. Both pregnant mother’s and their newborns should be monitored for signs of either infection or bleeding during or after pregnancy although these complications are rarely observed. You should definitely be followed by a maternal fetal medicine specialist during your pregnancy. Make sure you start taking prenatal vitamins if you haven’t already.

Good luck and congratulations

Revere (Rip) Kinkel MD
Director of the Multiple Sclerosis Program
Professor of Clinical Neurosciences
University of California San Diego