Ans. is 'd' i.e., Isotretinoin * Following is the risk category of the drugs to be used in pregnancy:Risk category of drugs during pregnancyCategoryExamplesA No riskAdequate studies in pregnant women have failed to demonstrate a risk to the foetusInj. Mag. sulfate, thyroxineB No evidence of risk in humansAdequate human studies are lacking, but animal studies have failed to demonstrate a risk to teh foetusorAdequate studies in pregnant women have failed to demonsirate a risk to the fectus, but animal studies have shown an adverse effect on the foetusPenicillin V. amoxicilin. cafactor, erythromycin, paracetamol, lidocaineC Risk cannot be ruled oldNo adequate studies in pregnant women and animal studies are lacking or have shown an adverse effect on foetus, but potential benefit may warrant use of the drug in pregnant women desplite potential riskMorphine, codeine, atropine, corticosteroids, adrenaline, thiopentone, bupivacaineD Benefit may out weight potential riskThere is evidence of human foetal risk, but the potential benefits from use of the drug may be acceptable despite the potential riskAspirin, phenytoin carbamazepine valproate, lorazepam, methotrexateX ContraindicatedStudies in animals of humans have demonstrated foetal abnormalities, and potential risk clearly outweighs possible benefitEstrogens, isotretinoin, ergometnne thalidomide* Category X drugs have proven fetal abnormalities and are teratogenic.