<prompt> Most common cause of HIV infection in infant is:Perinatal transmissionBreast milkTransplacementUmbilical cord sepsis  <response>: Ans. is a, Perinatal transmissionRef. COGDT 10e, p 692, 693; Dutta Obs. 7e, p 301, 302; Harrison 17e, p 1145; Williams Obs. 23e, p 1248 onwards, Dutta Obs. 7e, p 301-302Maternal transmission of HIV to child i.e. vertical transmission can occur:Antepartum TransplacentalPeripartum exposure to maternal blood and body fluids at delivery--Maximum risk periodPostpartum breastfeeding.Maximum risk of transmission is in peripartum period followed by labourIn the absence of any intervention, an estimated 15-30 of mothers with HIV infection will transmit the infection during pregnancy and delivery, and 10-20 will transmit the infection, through breastfeeding. Vertical transmission of HIV-1 occurs mostly during the intrapartum period 50-70 --COGDT 10e, p 692Note: If the choice is between intrapartum and peripartum period-better option is peripartum as the risk of transmission due to breastfeeding is also included in peripartum period. --Park 19e, p 289, 290Vertical transmission rate to neonates is ?14-25Factors increasing vertical transmission:Disease factors-Maternal viral load i.e. maternal plasma HIV RNA burden most important risk factor-Seroconversion in pregnancy or early disease-Advanced maternal disease-Low CD4 count i.e. risk of vertical transmission is inversely related to maternal immune status-Vitamin A deficiency-ChorioamnionitisObstetric factors-Vaginal delivery-Prolonged rupture of membranes 4 hrs-Preterm delivery-Chorioamnionitis-Coexistent STD specially HSV and syphilitic-Low birth weight infection of placenta-Antepartum invasive procedures amniocentesis, CVS, etc.-Intrapartum invasive procedures instrumental delivery, episiotomy, scalp electrodes, etc. 