Aortic dissection (AoD) during pregnancy is a rare but lethal condition and highlights the need for extensive elucidation. The aim of this study is to reveal the risk factors for AoD during pregnancy and to compare the 2 main risk factors, Marfan syndrome and pregnancy itself in the previously healthy woman. The pregnant patients developed AoD at 31.7 ± 7.6 weeks of gestation. It occurred much earlier in the Marfan patients than in the previously healthy women (30.7 ± 8.6 weeks of gestation vs 34.4 ± 4.4 weeks of gestation, P = 0.0263). In the Marfan patients, AoD developed in 3 (3.2%), 15 (15.8%), and 43 (46.3%) patients in the 3 trimesters, respectively, compared with 31 of the previously healthy women, and only in the third trimester. The neonates of the Marfan patients had better Apgar scores at 1 and 5 minutes, lower intubation rates, and fewer stays in the neonatal intensive care unit than those of the previously healthy women. Marfan syndrome and pregnancy itself in the previously healthy woman were the 2 main risk factors responsible for the occurrence of AoD during pregnancy. Marfan patients may develop AoD at an early age and an early stage of pregnancy, probably due to the preexisting weakened aortic wall. Better outcomes for the surviving neonates of Marfan patients compared with neonates of the previously healthy women might be the result of the poor condition of Marfan patients causing a higher death rate for those fetuses.