Tretinoin is a vitamin A derivative with antipsoriatic properties when applied topically as a come-dolytic agent with utility in acne vulgaris and in photodamaged skin and in treating premalignant skin conditions. In the laboratory, tretinoin was tested for developmental toxicity by the topical route, and the only consistent results have been obtained in the rabbit and hamster. In the human, four case reports identified tretinoin as a cause of congenital malformations following topical administration during pregnancy. A retrospective study comprised of 215 women exposed to tretinoin in early pregnancy compared to 430 controls found that the number of malformations in the exposed group was significantly less than in the control group. Tretinoin is a relatively large conjugated chemical that is highly hydrophobic as compared to the other compounds. Hydrogen bonding interactions can occur through the carboxylic acid portion of the molecule.