Further evidence against the reliability of the human chorionic gonadotropin discriminatory level

The human chorionic gonadotropin (hCG) discriminatory level-the maternal serum β-hCG level above which a gestational sac should be consistently visible on sonography in a normal pregnancy--has been reported to be 1000 to 2000 mIU/mL for transvaginal sonography. We assessed whether a woman with a β-hCG above 2000 mIU/mL and no intrauterine fluid collection on transvaginal sonography can subsequently be found to have a live intrauterine gestation and, if so, what the prognosis is for the pregnancy.

We identified all women scanned between January 1, 2000, and December 31, 2010, who met the following criteria: serum β-hCG testing and transvaginal sonography were performed on the same day; β-hCG was positive and sonography showed no intrauterine fluid collection; and a live intrauterine pregnancy was subsequently documented. We tabulated the β-hCG levels in these cases and assessed pregnancy outcome.

A total of 202 patients met the inclusion criteria, including 162 (80.2%) who had β-hCG levels below 1000 mIU/mL on the day of the initial scan showing no intrauterine fluid collection, 19 (9.4%) with levels of 1000 to 1499, 12 (5.9%) 1500 to 1999, and 9 (4.5%) above 2000 mIU/mL. There was no significant relationship between initial β-hCG level and either first-trimester outcome or final pregnancy outcome (P > .05, logistic regression analysis and Fisher exact test). The highest β-hCG was 6567 mIU/mL, and the highest value that preceded a liveborn term baby was 4336 mIU/mL.

The hCG discriminatory level should not be used to determine the management of a hemodynamically stable patient with suspected ectopic pregnancy, if sonography demonstrates no findings of intrauterine or ectopic pregnancy.