OBJECTIVE: To provide research basis and references for individual treatment of low-risk gestational trophoblastic disease（ LRGTN） with methotrexate.METHODS: The clinical symptoms of 3 LRGTN patients with obvious adverse reactions after the treatment of methotrexate were observed

the blood concentration of methotrexate

methylenetetrahydrofolate reductase（ MTHFR） and ATP binding cassette subfamily B member 1 transporter（ ABCB1）genotype were detected

discussion and analysis were conducted on blood concentration and gene polymorphism combined with therapeutic effect and adverse drug reactions.RESULTS: At 2-24 hours after intramuscular injection

the blood concentration of methotrexate was ranged from 1.132-0.012 μmol/L.In terms of the MTHFR C677 T genotype

2 patients were of CT type

and their ABCB1 T3435 C genotype was heterozygous mutant

with the adverse drug reactions were fever

bone marrow suppression

elevated liver function indicators and drug resistance; the other patient was CC type

with the adverse drug reactions were fever and rash.The MTHFR A1298 C genotypes of 3 patients were all wild-type.CONCLUSIONS: This study provides reference and basis for the individualized treatment of LRGTN with methotrexate.When methotrexate was used to treat LRGTN

its blood concentration was at a low level with no significant difference

and the significance of blood concentration detection needs to be further clarified

there is no obvious correlation between blood concentration and gene polymorphism

the gene polymorphism detection of MTHFR C677 T and ABCB1 T3435 C is of great significance for the selection of methotrexate

the prediction and management of adverse drug reactions.