What is ectopic pregnancy and what is the initial diagnostic approach?

• A. Implantation outside the uterus; investigate with transvaginal ultrasound and serial quantitative hCG
• B. Implantation inside the uterus; check estrogen levels
• C. Implantation in the ovary; MRI
• D. Implantation in the cervix; blood tests only

Answer: (A)

Ectopic pregnancy is when the embryo implants outside the uterus, most often in the fallopian tube. The initial diagnostic approach combines transvaginal ultrasound, which directly locates the pregnancy and looks for an adnexal mass or free fluid, with serial quantitative hCG measurements to track how the pregnancy is progressing. If there’s no intrauterine pregnancy seen on ultrasound when hCG levels are above the threshold where you’d expect to see one, or if the hCG fails to rise normally over 48 hours, that raises strong suspicion for an ectopic pregnancy. This dual approach works best because ultrasound provides direct localization while hCG patterns help interpret equivocal imaging and distinguish ectopic from a normal early intrauterine pregnancy. Estrogen levels, MRI, or blood tests alone don’t reliably diagnose ectopic pregnancy, and imaging-guided localization is essential for proper management.