Final answer:
The classic triad of an ectopic pregnancy includes unilateral pelvic pain, vaginal bleeding, and amenorrhea. These symptoms occur when a fertilized egg implants outside the uterus, often in a fallopian tube.
Step-by-step explanation:
The classic triad associated with an ectopic pregnancy is Option 1: UNI (unilateral) pelvic/low abdominal pain, vaginal bleeding, and amenorrhea (absence of menstrual period). This set of symptoms may indicate that a fertilized egg has implanted outside the uterus, most commonly in a fallopian tube, leading to a tubal pregnancy. Unilateral pain occurs because the ectopic pregnancy usually affects one side of the pelvis. Vaginal bleeding is often different from a normal period and can vary in severity. Amenorrhea occurs because the woman is technically pregnant, even though the pregnancy is not located in the uterus. If a patient presents with these symptoms, quick medical evaluation is necessary as an ectopic pregnancy can be life-threatening if not treated promptly.