['Since cyclophosphamide is metabolically activated to teratogenic acrolein and cytotoxic phosphoramide mustard by cytochrome P-450 type 2B (CYP2B), we assessed the effects of licorice, a CYP2B inducer, on the fetal defects induced by cyclophosphamide.', 'Pregnant Sprague-Dawley rats were daily administered with licorice (100\u2009mg/kg) by gavage for 7 days, from the 6th to 12th day of gestation, and intraperitoneally administered with cyclophosphamide (11\u2009mg/kg) 1\u2009hr after the final licorice treatment. On the 20th day of gestation, maternal and fetal abnormalities were determined by Cesarian section.', 'Cyclophosphamide was found to reduce fetal and placental weights without increasing resorption or death. In addition, it induced malformations in live fetuses; 93.8, 41.1, and 100% of the external (skull and limb defects), visceral (cleft palate and ureteric dilatation), and skeletal (acrania, vertebral/costal malformations, and delayed ossification) abnormalities, respectively. When pre-treated with licorice, cyclophosphamide-induced body weight loss and abnormalities of fetuses were remarkably aggravated. Moreover, repeated treatment with licorice greatly increased mRNA expression and activity of hepatic CYP2B.'] Does licorice extract increase cyclophosphamide teratogenicity by upregulating the expression of cytochrome P-450 2B mRNA?