The primary objectives of the study are to prospectively evaluate pregnancy complications and outcomes in participants with SMA, birth outcomes and adverse effects in infants born to participants with SMA, who were exposed to nusinersen up to 14 months prior to the first day of their last menstrual period (LMP) before conception, 14.5 months before the date of conception, and/or at any time during their pregnancy. The secondary objective of the study is to evaluate pregnancy outcomes in participants with SMA exposed to nusinersen as compared with participants without SMA who were not exposed to nusinersen (e.g., participants from external, general population comparators).