Which of the following best explains why Lignocaine has a higher fetal-to-maternal plasma ratio when compared with bupivacaine?: (A) Bupivacaine has low molecular weight, (B) Lignocaine has higher protein-binding, (C) Bupivacaine has a lower dissociation constant (pKa), (D) Lignocaine is less protein bound
Answer is D. Lignocaine is  less protein bound than bupivacaine. Unbound form of drug thus easily gets transferred across placenta.