Inclusion Criteria:  Participants must meet all the criteria listed under the respective cohorts to enroll in that particular cohort of the registry:  Cohort 1: Siponimod-Exposed Cohort  Pregnant women Diagnosed with MS, with the indication validated by medical records when possible Exposure to siponimod for the treatment of MS, for any number of days, at any dose, and at any time from the 4th day post the first day of LMP prior to conception up to and including the end of pregnancy Agree to the conditions and requirements of the study including the interview schedule, release of medical records, the dysmorphology examination of live born infants, and the Ages and Stages Questionnaire (ASQ) in live born children  Cohort 2: Disease-Matched Comparison Cohort (Comparison Group 1)  Pregnant women Diagnosed with MS, with the indication validated by medical records when possible May or may not have taken another medication for MS in the current pregnancy Agree to the conditions and requirements of the study including the interview schedule, release of medical records, the dysmorphology examination of live born infants, and the ASQ in live born children  Cohort 3: Healthy Comparison Cohort (Comparison Group 2):  Pregnant women Agree to the conditions and requirements of the study including the interview schedule, release of medical records, the dysmorphology examination of live born infants, and the ASQ in live born children  Exclusion Criteria:  Women meeting any of the following criteria will be excluded from the cohort study:  Cohort 1: Siponimod-Exposed Cohort  Women who have enrolled in the siponimod cohort study with a previous pregnancy Women who have used siponimod for an indication other than a currently approved indication  Women with exposure to any of the following medications within 5 half-lives prior to conception:  Cladribine (Mavenclad) Based on the US label, animal studies indicate that there is positive evidence of teratogenicity for Cladribine All other S1P modulators including fingolimod (Gilenya), ozanimod, etc. S1P modulatros are in the same class of drug as siponimod Teriflunomide (Aubagio) The teratogenicity of teriflunomide is unknown and currently under investigation New medications (marketed after 2020) indicated for the treatment of MS will be evaluated for inclusion/exclusion criteria as the study progresses. Retrospective enrollment after the outcome of pregnancy is known (i.e. the pregnancy has ended prior to enrollment) Results of a diagnostic test are positive for a major structural defect prior to enrollment. However, women who have had any normal or abnormal prenatal screening or diagnostic test prior to enrollment are eligible as long as the test result does not indicate a major structural defect.  Cohort 2: Disease-Matched Comparison Cohort (Comparison Group 1):  Exposure to siponimod any time from the 4th day post the first day of LMP prior to conception up to and including end of pregnancy  Women with exposure to any of the following medications within 5 half-lives of conception:  Cladribine (Mavenclad) S1P modulators Teriflunomide (Aubagio) New medications (marketed after 2020) indicated for the treatment of MS will be evaluated for inclusion/exclusion criteria as the study progresses. Women who have enrolled in the siponimod cohort study with a previous pregnancy Retrospective enrollment after the outcome of pregnancy is known (i.e. the pregnancy has ended prior to enrollment) Results of a diagnostic test are positive for a major structural defect prior to enrollment. However, women who have had any normal or abnormal prenatal screening or diagnostic test prior to enrollment are eligible as long as the test result does not indicate a major structural defect.  Cohort 3: Healthy Comparison Cohort (Comparison Group 2):  Exposure to siponimod any time from the 4th days post first day of LMP prior to conception to and including end of pregnancy Women who have a diagnosis of a MS or a siponimod approved indication Women who have a current diagnosis of any autoimmune disease Women who have first contact with the project after prenatal diagnosis of any major structural defect Women who have enrolled in the siponimod cohort study with a previous pregnancy Retrospective enrollment after the outcome of pregnancy is known (i.e. the pregnancy has ended prior to enrollment) Results of a diagnostic test are positive for a major structural defect prior to enrollment. However, women who have had any normal or abnormal prenatal screening or diagnostic test prior to enrollment are eligible as long as the test result does not indicate a major structural defect. Women exposed to a known human teratogen during pregnancy as confirmed by the OTIS Research Center