Relationship of high pretreatment folic acid level and failure of methotrexate in ectopic pregnancy: A pilot study

OBJECTIVE: To test the hypothesis that high (≥20.7 ng/mL) pretreatment serum folic acid level increases the failure of single-dose methotrexatefor ectopic pregnancy. STUDY DESIGN: Twenty patients with ectopic pregnancy and measured pretreatment folic acid levels were divided into 2 groups based on pretreatment serum folk acid level (< or ≥20.7 ng/mL). All patients were candidates for single-dose methotrexate treatment. Variables analyzed in the 2 groups were pretreatment folic acid level, initial β-human chorionic gonadotropin (hCG) level, size of the ectopic mass, presence of fetal heart tones and clinical outcomes. RESULTS: Eleven patients had serum folic acid levels < and 9≥20.7 ng/mL. The mean (±SD) folic acid level was 13.4 ng/mL (±3.2) in the group with folic acid levels <20.7 ng/mL, significantly lower than in the group with folic acid levels >20.7 ng/mL (p<0.001). The 2 groups were similar in initial hCG level, size of the ectopic mass and presence of fetal heart tones. The failure rate was significantly higher in the group with pretreatment serum folic acid levels ≥ 20.7 ng/mL as compared to the group below (n = 4, 44%, vs. n = 0, 0%; p = 0.02). CONCLUSION: High pretreatment folic acid levels increase the risk of treatment failure with single-dose methotrexate.