Beta HCG levels after conservative treatment of ectopic pregnancy: is a plateau normal?

In 32 women with unruptured tubal ectopic pregnancies we undertook conservative laparoscopic treatment [local injection of 20 mg methotrexate (n = 18), laser salpingotomy (n = 14)]. The results of serial quantitative beta HCG measurement were followed until either a negative level was reached or until rising levels necessitated alternative/additional therapy. Plateaued values of beta HCG were observed in both the successful (n = 16) and the unsuccessful cases (n = 5). To test the hypothesis that daily variation in the assay could account for some or all of the observed plateaued results in successful cases, the sera were retested serially on the same 'run'. In only one case did laboratory variation account for the observed plateau. The clinical implications of the findings are discussed. We conclude that serially monitored beta HCG results after conservative treatment of ectopic pregnancy may show plateaued values without indicating failure of treatment.