Condous et al used the ratio of serum HCG specimens collected at 0 and 48 hours to evaluate women with pregnancies of unknown location (PUL). This ratio can help determine if an intervention is appropriate. The authors are from St. George's University in London and K.U. Leuven in Belgium.


Criteria for a pregnancy of unknown location (PUL):

(1) positive pregnancy test

(2) no signs of intra- or extra-uterine pregnancy on transvaginal ultrasonography

(3) absence of miscarriage remnants


HCG ratio =

= (serum HCG ratio at 48 hours) / (serum HCG ratio at 0 hours)



• A ratio <0.87 defined "failing" PUL. These patients can usually be managed by a noninterventional strategy.

• A ratio >= 0.87 defined a "persistent" PUL. These patients typically were treated with a single dose of methotrexate, which was followed by decline of the HCG level.


To read more or access our algorithms and calculators, please log in or register.