The objective of this study was to determine whether a single or repeated injection of methotrexate (MTX) to treat ectopic pregnancy results in either teratogenicity or other bad obstetric outcome in the pregnancy that shortly follows treatment. Data were retrieved from the medical records of 314 women treated with MTX for ectopic pregnancy in our institute (2000-2006) included age, MTX dosage, interval between last MTX treatment to conception, results of ultrasonographic follow-up of the subsequent pregnancy, triple test, karyotype testing, pregnancy outcome, and newborn weight and Apgar score. A logistic regression model based on pregnancy outcome as the dependent variable and interval since last MTX treatment as the independent variable estimated the odds ratio for the safety of conception occurring shortly after the treatment. Complete information was obtained for 125 pregnancies. Forty-five pregnancies occurred within 6 months (mean 3.6+/-1.7) after the last MTX treatment. The outcome of these pregnancies was compared with that of 80 pregnancies which occurred > or =6 months (mean 23.6+/-14.7) after the last MTX treatment. The fetal malformation and adverse outcome rates for both groups were similar (odds ratio 1.003, 95% CI 0.98-1.02). According to a logistic regression analysis, the interval between the last MTX treatment for ectopic pregnancy had no effect on the outcome of the pregnancy that shortly followed it. The results of this study support the notion that conceiving within the first 6 months after treatment with MTX for ectopic pregnancy is safe and not associated with any increase in the examined adverse pregnancy outcome parameters.