Pregnancy determination may be made within 3 to 4 weeks' gestational age using radioimmunoassay or two-site ELISA assay. Using serum progesterone concentrations, serial quantitative beta-hCG levels, culdocentesis, sonography, laparoscopy, and fetal heart rate determination, the clinician is able to determine fetal viability and implantation site often within 6 to 7 weeks' gestational age. Improved sensitivity in diagnostic modalities, as well as increased awareness of the often subtle clinical findings in ectopic pregnancy are probably both responsible for the decline in morbidity and mortality seen with ectopic pregnancy over the past 25 years. As the incidence has seen an even greater increase than this decline, however, ectopic pregnancy remains the leading cause of first-trimester maternal mortality in this country. With the use of imaging in pregnancy, the question of fetal safety must also arise. The modalities currently used in the first trimester of pregnancy appear to pose minimal risks to the developing fetus if used only when necessary, and then with caution.