In addition to discontinuing the oral contraceptive in preparation for attempting conception, fingolimod should be stopped. An oral disease-modifying therapy for multiple sclerosis (MS), fingolimod is a sphingosine-1-phosphate receptor modulator that restricts activated lymphocytes to lymph nodes and may also have direct neuroprotective effects. Fingolimod significantly reduces the relapse rate, risk of disability progression, and accumulation of new lesions on MRI. This drug has been associated with rare but potentially harmful side effects, including increased rates of serious herpesvirus infection, hypertension, bradycardia, lymphopenia, liver function abnormalities, and macular edema. Fingolimod is classified as a pregnancy category C drug, and thus its safety in human pregnancy is not clearly established. Although category C medications are indicated in some patients if the benefits outweigh the risks, the hormonal state of pregnancy itself is protective against MS activity, and thus discontinuing a disease-modifying drug during pregnancy is considered relatively safe.

Advising this patient against pregnancy is clearly inappropriate. The adverse effect of pregnancy on MS progression is a commonly held misconception. In fact, observational studies have found reduced risks for conversion to clinically definite MS from clinically isolated syndromes and reduced risks for conversion from relapsing MS to secondary progressive MS in women with multiple pregnancies.

Mitoxantrone is an anthracenedione chemotherapeutic agent that reduces lymphocyte proliferation and decreases the relapse rate and disability progression in MS. Despite mitoxantrone's efficacy, cardiac toxicity and the risk of secondary leukemia have significantly limited its use. Mitoxantrone is classified as a pregnancy category X drug and is contraindicated during pregnancy.

The MS drug teriflunomide is the active metabolite of leflunomide, which inhibits pyrimidine biosynthesis and interferes with the interaction between T lymphocytes and antigen-presenting cells. Substituting teriflunomide for fingolimod is inappropriate because teriflunomide is classified as pregnancy category X drug and is contraindicated during pregnancy.