Final answer:
Unilateral stabbing lower abdominal pain best supports a possible ectopic pregnancy in a client with a positive pregnancy test.
Step-by-step explanation:
Lower abdominal pain in a client with a positive pregnancy test can be indicative of an ectopic pregnancy. The best supporting symptom for a possible ectopic pregnancy in this scenario would be unilateral stabbing lower abdominal pain. While other options like edematous face, hands, and ankles or steady bleeding with lower abdominal pain may be seen in certain pregnancy complications, the presence of unilateral stabbing pain is more specific to ectopic pregnancy.