There are many situations in which the earliest possible detection of an intrauterine pregnancy would enhance clinical management. Current radioimmunoassays for hCG can detect pregnancy as early as eight to 12 days postconception. The ability to document an intrauterine pregnancy with ultrasound has lagged behind by two to three weeks. New high-frequency endovaginal transducers offer the promise of narrowing this gap. This study was undertaken prospectively on 235 patients all amenorrheic for seven weeks or less and requesting either pregnancy testing or termination. All had endovaginal ultrasound scans. We obtained hCG levels when no sac was seen or when the sac was less than 1.0 cm (initial experience revealed that all sacs over 1.0 cm were associated with hCG levels over 6000 mlU/mL) (International Reference Preparation). Ultrasound findings were, correlated with pathology specimens and/or hCG levels where appropriate. Results indicated that normal pregnancies can be.imaged when: 1) The sac is greater than 0.4 cm; 2) hCG is greater than 1025 mlU/mL (International Reference Preparation); and 3) the uterus is normal with a homogeneous echo pattern. This was not true in three of our cases with diffuse myomatous changes or a coexisting intrauterine device.
© 1988 The American College of Obstetricians and Gynecologists