This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Anaesthesia
Most impoant factor determining the affect of anaesthetic agent on fetus 
Select and explain. 
A. Duration of pregnancy, B. MAC, C. Protein binding, D. Route of anaesthetic
A: Duration of pregnancy
Answer: A: Duration of pregnancy 
Explanation: All the given options determined the effect of anaesthetic on fetus. But, duration of pregnancy is the most impoantAlmost all anaesthetic agents can be potentially teratogenicDay 15th to day 60 is the most critical period.(Refer: Morgan and Mikhail's Clinical Anaesthesiology, 5th edition, pg no. 846)