Objective: To identify risk factors for tubal rupture among ectopic pregnancies treated with methotrexate (MTX).
Design: Retrospective case-control analysis.
Setting: An urban medical center.
Patient(s): Eighty-one women diagnosed with an ectopic gestation treated with MTX: 19 patients experienced subsequent tubal rupture, and 62 patients experienced ectopic resolution.
Intervention(s): None.
Main outcome measure(s): Predictive variables including serial human chorionic gonadotropin (hCG) values.
Result(s): The hCG incremental rate before as well as after MTX administration was positively associated with tubal rupture. HCG values prior to ectopic diagnosis that increased at least 66% over 48 hours and rising hCG values after treatment with methotrexate were independent predictors of tubal rupture. A disproportionate number (47%) of ectopic pregnancies that ruptured were located in the tubal isthmus.
Conclusion(s): The hCG incremental rate both before and after MTX represents an independent risk factor for subsequent tubal rupture. Concentrations of hCG before ectopic diagnosis that increased at least 66% over 48 hours, or persistently rising hCG concentrations after treatment with MTX, may lower the threshold for surgical intervention. Implantation site may represent an unidentifiable risk factor for tubal rupture.