Considering that multiple sclerosis (MS) affects primarily women of childbearing age, it comes as no surprise that for many patients MS and pregnancy often occur together. The issues to consider when discussing pregnancy and MS include:
- How pregnancy affects MS
- How MS affects pregnancy
- How MS treatment should be managed throughout pregnancy
The Pregnancy in MS (PRIMS) study of 254 patients revealed that pregnancy is generally protective against MS relapses, in particular during the third trimester. In contrast, the same study found a rebound of relapses during three months post delivery, with 30 percent of women experiencing a relapse within three months after delivery. Several strategies have been proposed to avert the risk of postpartum relapse, including the use of prophylactic IVIG or corticosteroids. More recently, exclusive breast-feeding has been found to offer some protection against postpartum MS activity; however, this finding was disputed in a subsequent study.
There is no evidence that MS impairs fertility or leads to an increased number of spontaneous abortions, stillbirths or congenital malformations. MS also does not increase a woman’s risk of preeclampsia or premature rupture of membranes. Pregnant women with MS are 1.3 times more likely to undergo antenatal hospitalization and to have a Cesarean delivery, and they are 1.7 times more likely to have infants who are small for gestational age 6.
Except for glatiramer acetate, all MS disease-modifying treatments (DMT) have documented in utero harmful effects in animal studies and are therefore FDA pregnancy category C agents. Glatiramer acetate is a category B agent and is not known to have harmful effects in animal studies, although human studies are lacking.
For these reasons, the National MS Society and most MS specialists advise women who intend to become pregnant to discontinue therapy. Given their pharmacokinetics, we suggest the following schedule based on the type of therapy: one month (glatiramer), two months (fingolimod) or three months (interferons, natalizumab) prior to anticipated conception. It is less clear when to resume the therapy following the delivery.
Because only a minuscule amount of medications is excreted in mother’s milk, some MS specialists advise patients to resume therapy – with the exception of fingolimod or natalizumab – as soon as possible, even in women who intend to breast-feed. In the event of an MS relapse during or after the pregnancy, treatment with high dose intravenous methylprednisolone is generally considered safe for both mother and baby.