What is a significant risk factor for pulmonary embolism shortly after delivery?

The correct choice, recent surgery, is a significant risk factor for pulmonary embolism shortly after delivery due to the increased likelihood of venous thromboembolism (VTE) associated with surgical procedures. Surgery can lead to venous stasis, endothelial injury, and a hypercoagulable state, all contributing to a heightened risk of blood clot formation. After delivery, especially if a cesarean section was performed, the risk is further amplified as the body is still recovering, and the flow of blood can be disrupted.

Other options may have some relevance to overall risk factors for VTE, but they do not carry the same immediate significance in relation to pulmonary embolism shortly after delivery. Prolonged labor can contribute to complications but is not as directly associated with VTE as recent surgical intervention. Being nulliparous (having never given birth) might indicate a certain demographic risk, but it is not a specific risk factor for developing pulmonary embolism in the postpartum period. Obesity is indeed a risk factor for complications such as VTE, but recent surgery stands out as a more acute and pressing risk immediately following delivery.