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: Gynaecology & Obstetrics
Which Ig crosses through placenta: September 2008 
Select and explain. 
A. IgA, B. IgE, C. IgG, D. IgM
C: IgG
Answer: C: IgG 
Explanation: Ans. C: IgG IgG is the only isotype that can pass through the human placenta, thereby providing protection to the fetus in utero. Along with IgA secreted in the breast milk, residual IgG absorbed through the placenta provides the neonate with humoral immunity before its own immune system develops. Colostrum contains a high percentage of IgG,