Single best prognostic indicator of successful treatment with single-dose Methotrexate is
Gestational sac size
Serum b-hCG level
Absence of fetal cardiac activity
Pain abdomen
The best candidate for medical therapy is the woman who is asymptomatic, motivated, and compliant. With medical therapy, some classic predictors of success include a low initial serum b-hCG level, small ectopic pregnancy size, and absent fetal cardiac activity. Of these, initial serum b-hCG level is the single best prognostic indicator of successful treatment with single-dose MTX. Specifically, repoed failure rates are 1.5 percent if the initial serum b-hCG concentration is <1000 mIU/mLReference: William's Obstetrics; 25th edition; Chapter 19; Ectopic pregnancy
General obstetrics