At which point in pregnancy does a woman have the greatest risk of a dissecting aneurysm?

The highest risk of a dissecting aneurysm during pregnancy is observed in the third trimester. This increased risk is primarily linked to the physiological and anatomical changes that occur as the pregnancy progresses.

During the third trimester, significant hormonal and vascular adaptations take place in preparation for childbirth. These adaptations can lead to increased hemodynamic stress on vascular structures, particularly major arteries. The expanding uterus can also exert pressure on surrounding blood vessels, which could contribute to the risk of vascular complications, including dissections. Furthermore, a woman's body experiences increased blood volume and cardiac output, which further influences the dynamics of blood flow and vascular integrity.

Additionally, pre-existing conditions that may predispose a woman to vascular issues, such as hypertension or connective tissue disorders, can worsen during this stage of pregnancy. Therefore, the combination of hormonal changes, mechanical pressure, and pre-existing conditions creates a perfect storm for cardiovascular complications, making the third trimester the period of greatest concern for dissecting aneurysms.

While there are risks associated with other trimesters and even postpartum, they do not match the heightened risk seen in the third trimester when both fetal development and maternal physiological changes are at their peak.