Cytarabine is a purine antimetabolite used therapeutically as an antineoplastic agent, as it is active in treating leukemia and lymphoma. Its mechanism of action is by inhibition of DNA synthesis, through conversion to its active compound, aracytidine triphosphate, which is incorporated into DNA, inhibiting DNA polymerase and resulting in decreased DNA synthesis and repair; it is rapidly metabolized. Among animal studies, cytarabine is teratogenic, and it increased fetal mortality and inhibited fetal body weight when given to mice during the organogenesis period of gestation. Paternal use of cytarabine combined with other antineoplastic drugs prior to conception was said to result in congenital anomalies. Based on the number of published cases of unaffected infants born following first trimester exposure to cytarabine the risk for developmental toxicity in the human associated with cytarabine is rather high, especially due to intrauterine death, at approximately 64%. Cytarabine is a hydrophobic chemical of near average size as compared with the other human developmental toxicants.