Stop using the hCG discriminatory zone of 1,500 to 2,000 mIU/mL to guide intervention during early pregnancy

When a gestation is found to be nonviable A viable intrauterine pregnancy is highly unlikely in a woman with no ultrasound evidence of an intrauterine pregnancy or an adnexal mass and an hCG level that rises very little, plateaus, or decreases over 48 hours. In this situation, a Karman cannula aspiration of uterine contents with rush pathology analysis can help clarify the likely diagnosis and guide therapy.

Women with documented ­villi on pathology likely are experiencing a miscarriage and can have their hCG level followed to resolution. Women with no documented villi and no decrease in hCG after the Karman
cannula aspiration can be presumed to have an ectopic pregnancy. If stable, these women may be candidates for treatment with methotrexate.^8,9

Many experts have counseled against the use of a single hCG measurement in the discriminatory zone of 1,500 to 2,000 mIU/mL to trigger methotrexate treatment. Here is a sampling of their advice:

“An hCG level of 2,000 mIU/mL, without ultrasound findings of intrauterine pregnancy, while suggestive of abnormal pregnancy, is not diagnostic. Per the results of recent studies, it is reasonable to closely follow up rather than treat many of these early, stable cases of ectopic pregnancy.”
—Mehta et al.¹

“Our data demonstrate that using a single value of serum hCG in a pregnancy of unknown location (PUL) population is of limited value.... A significant proportion of failing PULs and early intrauterine pregnancies in a PUL population have high serum hCG levels at presentation.”
—Condus et al.²

“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.”
—Doubilet et al.³

“There is almost no reason to give methotrexate on first encounter with a patient. If a patient is symptomatic with severe pain or signs of rupture, a surgical approach is indicated and methotrexate is contraindicated.”
—Barnhart et al.⁴

[When using the discriminatory zone]... “there is a chance of harming a viable intrauterine pregnancy, especially if the hCG level is 2000 to 3000 mIU/mL.... There is limited risk in taking a few extra days to make a definitive diagnosis in a woman with a pregnancy of unknown location who has no signs or symptoms of rupture and no ultrasonographic evidence of ectopic pregnancy.”
—Doubliet et al.³