Tysabri and Pregnancy
At this time, it is unknown if it is safe for pregnant women to receive Tysabri (natalizumab). Although this medicine has not been studied in pregnant women, animal studies suggest the drug could increase the risk of miscarriages or blood cell problems. Due to the potential risks, pregnant women should only receive this medicine if the benefits outweigh the risks.
Can Pregnant Women Receive Tysabri?Tysabri® (natalizumab) is a prescription medication approved to treat people who have relapsing multiple sclerosis (when the condition has periods of worsening symptoms, or flare-ups). It is also approved to treat people with moderate-to-severe Crohn's disease. Based on the results of animal studies, this medication may not be safe for use during pregnancy.
What Is Pregnancy Category C?Tysabri is classified as a pregnancy Category C drug. The U.S. Food and Drug Administration (FDA) uses a category system to classify the possible risks to a fetus when a specific medicine is taken during pregnancy. Pregnancy Category C is given to medicines that have not been adequately studied in pregnant humans but have caused fetal harm in animal studies.
In addition, medicines that have not been studied in any pregnant women or animals are automatically given a pregnancy Category C rating.
Tysabri has not been adequately studied in pregnant women. In animal studies, this drug did not appear to cause birth defects. However, it did cause miscarriage when given in high doses to pregnant guinea pigs and monkeys. It also caused blood cell problems in the offspring of the monkeys, including low red blood cell and platelet counts.
However, it is important to note that animals do not always respond to medicines in the same way that humans do. Therefore, a pregnancy Category C medicine may be given to a pregnant woman if the healthcare provider believes that the benefits to the woman outweigh any possible risks to her unborn child.