At what gestational age is zidovudine typically initiated in newly diagnosed HIV-positive pregnant women?

Zidovudine is typically initiated in newly diagnosed HIV-positive pregnant women at around 14 weeks gestation. This timing is crucial for minimizing the risk of mother-to-child transmission of the virus during pregnancy. Starting treatment at this point allows sufficient time for the drug to be effective in reducing the viral load in the mother, thereby lowering the chances of transmission during childbirth and in the postpartum period.

Beginning treatment earlier, such as at 10 weeks gestation, is not standard practice because the risk of HIV transmission is already considered to be significantly reduced when treatment is started around 14 weeks. Also, starting zidovudine in the third trimester may not provide the necessary time for the drug to be fully effective, potentially leaving the infant at risk during the delivery process. Initiating treatment during labor is too late to achieve any meaningful reduction in viral load that could impact transmission risk.

Thus, the recommended timing for initiation of zidovudine in pregnant women with HIV is at approximately 14 weeks gestation to ensure both maternal health and the health of the infant.