At What β-hCG Levels Should Viable Pregnancies Be Consistently Detectable by Ultrasound?

The evaluation of women who present with first-trimester pain or vaginal bleeding typically includes measurement of serum levels of beta human chorionic gonadotropin (β-hCG) and transvaginal ultrasonography to determine the likelihood of a viable intrauterine pregnancy. β-hCG levels of 1500 to 2000 milli-international units per milliliter (mIU/mL) are typically considered to define the “discriminatory zone” within which evidence of a viable fetus should be consistently detected on ultrasound. However, this zone was defined in women with uncomplicated pregnancies before important advances in ultrasound technology. To address these drawbacks, investigators conducted a retrospective cohort study of data collected from a single university hospi…