Peter Michael Doubilet MD, PhD, Presenter: Nothing to Disclose

Carol Beer Benson MD, Abstract Co-Author: Nothing to Disclose

The hCG discriminatory level – the maternal serum hCG level above which a gestational sac should be consistently visible on ultrasound in a normal intrauterine pregnancy – has been reported to be 1000-2000 mIU/ml for transvaginal sonography. We conducted a study to assess whether a woman with a β-hCG above 2000 mIU/ml and no intrauterine fluid collection seen on transvaginal sonography can subsequently be found to have a live intrauterine gestation and, if so, what the prognosis is for such a pregnancy.

We reviewed our ultrasound and hospital databases to identify all women scanned between 1/1/2000 and 12/31/2010 who met the following criteria: serum β-hCG and transvaginal ultrasound were performed on the same day; the β-hCG was positive and the ultrasound showed no intrauterine fluid collection; a live intrauterine pregnancy was subsequently documented. We tabulated the β-hCG levels in the study cases and assessed pregnancy outcome.

202 patients met the inclusion criteria for our study, 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 1000-1499, 12 (5.9%) 1500-1999, and 9 (4.5%) at or above 2000. There was no significant relationship between initial β-hCG level and either first trimester outcome or final pregnancy outcome (p> 0.05 [logistic regression analysis and Fisher exact test] for both first trimester and final pregnancy outcome). 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 ultrasound demonstrates no findings of an intrauterine or ectopic pregnancy.

Many emergency departments rely on the hCG discriminatory level to manage patients with suspected ectopic pregnancy, but our results indicate that this can harm normal intrauterine pregnancies

Doubilet, P, Benson, C, Further Evidence against the Reliability of the hCG Discriminatory Level.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11004099.html