October 9, 2018
Many women with multiple sclerosis are diagnosed during childbearing years. They ask about their risks concerning the disease during pregnancy and the risk for their children.
Women with MS have uncomplicated pregnancies and deliveries from OB perspective. They worry about their chance of disease progression with new relapses during pregnancy. They wonder about stopping their disease modifying medications, (DMT ), and risk of relapse. They question whether the medication will harm their fetus.
It has been known since the PRISMS study in 1998 that pregnancy is an immune privileged time for women with MS. The risk of relapse decreases in pregnancy, especially in the third trimester. There was an increased risk of relapses in first 3 months postpartum especially in woman who had active disease prior to pregnancy or relapse in pregnancy. However, 72% women had no relapse.
Now that patients are on DMT, they worry about relapses when medication is stopped. Maternal medications may cross the placenta barrier and are, therefore, a consideration when planning conception.
Risk of transfer depends on molecular size. Copaxone and interferons are large molecules that do not cross placenta until third trimester and have never caused fetal problems. The monoclonal antibodies, tysabri and ocrevus are not transported across placenta until third trimester when other maternal antibodies cross. None of these medications need to be stopped prior to conception.
Tysabri used to be stopped 2 months prior to wanting to conceive but recent studies showed that more relapses occurred in the first trimester, about time drug had been out of maternal circulation for too long. They showed that if tysabri is stopped when woman finds out she is pregnant, the risk of relapse goes down.
The oral medications, gilenya and tecfidera are small molecules and can cross the placenta. Women who got pregnant on gilenya have been showed to have an increased risk of fetal malformations compared to normal population. We recommend a 2 month washout for both medications prior to conception.
Women with MS have healthy babies and carry full term. They just need to consider their risk of relapse and potential risks for baby prior to planning conception. We want to keep both mother and fetus healthy and work with woman’s obstetrician toward that goal.
Nancy Nealon, MD