This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
Which of the following statements regarding transfer of drugs across placenta is FALSE ? 
Select and explain. 
A. Transfer across placenta is lesser in early pregnancy, B. All drugs to some extent can cross the placenta except heparin and insulin, C. Ion trapping of acidic drugs occur in the placenta, D. P–glycoprotein is present in placenta
C: Ion trapping of acidic drugs occur in the placenta
Answer: C: Ion trapping of acidic drugs occur in the placenta 
Explanation: Heparin and insulin are anticoagulant and antidiabetic drugs of choice, respectively in pregnancy becasue these have minimum entry across placenta
Fetal plasma is slightly more acidic than that of mother (pH 7.0 as compared to 7.4 of mother), so ion trapping of basic drugs occur.
Placenta contain P-glycoprotein that can act as an efflux pump for drugs.
Placental transfer of most drugs is greater in late pregnancy than in early pregnancy because uterine circulation increases and trophoblastic layer becomes thinner as the pregnancy advances.