The discriminatory zone of beta-hCG for vaginal probes.

Recent developments in both laboratory measurements and ultrasound technology have revolutionized the management of early pregnancy. The discriminatory zone concept is a direct result of these developments. By correlating the serum beta-hCG values to the size of an intrauterine gestational sac, a value can be chosen that corresponds to the threshold of visualization of the sac. If the beta-hCG is above this value, a sac must be seen, and if it is not, aggressive steps should be taken to determine whether the pregnancy is abnormal or ectopic. The discriminatory zone may vary among institutions due to different equipment and assays. Thus, its value should be calculated individually at each institution. A proper discriminatory zone and a management protocol such as the one above can eliminate much of the uncertainty in the management of suspected ectopic and early pregnancies.