This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Infections in pregnancy, Subject name: Gynaecology & Obstetrics
The maximum chances of HIV infection being transmitted to the fetus/ infant in an HIV infected mother are during: 
Select and explain. 
A. First trimester, B. Second trimester, C. Peripaum, D. During breastfeeding
C: Peripaum
Answer: C: Peripaum 
Explanation: Veical transmission of HIV (out of total 100 %) before 36 weeks: 20 % days before delivery: 50 % intrapaum: 30 % The risk of transmission during breast feeding may be as high as 30-40%. Also note that at all stages, risk of HIV transmission is directly related to maternal HIV viral load. Therefore maximum risk , out of given options is peripaum (days before delivery + intrapaum + immediate post paum) So to bring this infection rate less than 2 % all the HIV positive pregnant woman are staed on anti-retroviral (A) drugs irrespective of CD 4 count throughout pregnancy.