Which of the following symptoms would most likely indicate a serious complication in a pregnant woman?

Severe abdominal pain during pregnancy is a symptom that warrants immediate attention and could indicate a serious complication. This type of pain may suggest various conditions, such as an ectopic pregnancy, placental abruption, or preterm labor, any of which can pose significant risks to both the mother and the fetus. The abrupt onset or intensity of the pain can signal emergencies that need to be evaluated promptly.

In contrast, fatigue and morning nausea can frequently occur during pregnancy due to hormonal changes and are typically not immediate indicators of serious complications. Swelling of the ankles, while it can be concerning if it occurs alongside other symptoms, can also be common in normal pregnancies due to increased blood volume and pressure on the lower extremities. Thus, while monitoring these symptoms is essential, they do not carry the same immediate red flag as severe abdominal pain.