The P-450 enzymes usually catalyze oxidative metabolism ofxenobiotics as a part of the process of inactivation and elimination from thebody. The activity of CYP enzymes may sometimes lead to the formationof reactive metabolites with toxic or carcinogenic consequences. It hasbecome evident that xenobiotics-metabolizing CYP enzymes may also beinvolved in vital cell functions affecting growth, differentiation andhomeostasis.About 150 compounds that could be characterized as P AH were foundin tobacco smoke and hundreds were found in surrounding environment.Chemical constituents of P AH readily cross the placenta and producevarious forms of embryo toxicity such as small-for-date babies andintrauterine demise (miscarriage and stillbirth). Furthermore, the combinedeffect of intrauterine growth retardation and premature delivery perhapscoupled with 10-fold increase in the rate of infant mortality in the exposedmothers.Retinoids, metabolites of vitamin A, have been of interest todevelopmental biologists for many decades because of their teratogeniceffects on fetal development.Our study aimed to investigate the effect of the prior exposure of thepregnant mother to drug metabolizing enzyme inducer on the teratogeniceffect of known teratogen, include study the effect of 3-methylcholanthreneon the liver drug metabolism of pregnant mother and her fetuses and theeffect of known teratogen (all-Trans retinoic acid) on fetuses from 3