BACKGROUND: The risk of pregnancy-associated vascular complications in Marfan syndrome (MFS) is uncertain because of ascertainment bias, prepartum lack of knowledge of diagnosis, and insufficient peripartum imaging data. Furthermore, U.S. and European guidelines differ in pregnancy recommendations in MFS. OBJECTIVES: This study describes a single-center experience of 169 MFS women to address these gaps. METHODS: Clinical, imaging, and pregnancy history were compared in never vs ever-pregnant MFS women, and pregnancy-associated vascular complications were described. RESULTS: A total of 74 ever-pregnant women had 112 live births. Elective aortic root replacement occurred at a younger age in never-pregnant women (33 years vs 42 years; P = 0.0026). Although aortic dissection prevalence did not differ between never-pregnant vs ever-pregnant women (23% vs 31%; P = 0.25), it tended to occur at an earlier age in the former group (38 years vs 45 years; P = 0.07). Of observed "sanctioned" pregnancies with prepartum diameters ≤4.5 cm, mean pregnancy-related aortic diameters remained stable. In total, 5 dissections were associated with pregnancy: 2 type A in women unaware of their diagnosis; and 2 type B and 1 isolated coronary artery dissection in women aware of their diagnosis. Dissection rates were 5-fold higher in the pregnancy vs nonpregnancy period. CONCLUSIONS: Pregnancy-related type A dissection only occurred in patients unaware of their diagnosis. Type B dissection remains an unpredictable complication. Although there were baseline differences between the never- and ever-pregnant groups, no difference in dissection risk was observed outside the peripartum period. Those with prepartum aortic diameters between 4.0 and 4.5 cm demonstrated stable aortic dimensions throughout pregnancy. These findings provide a rationale to update existing U.S. guidelines for the management of pregnancy in MFS.