Highly active antiretroviral therapy is currently recommended for HIV-1 infected pregnant women for the management of maternal HIV infection and for prevention of perinatal HIV transmission. Many physiological changes occur during pregnancy may lead to changes in pharmacokinetics of drugs. Some of these pharmacokinetic changes may include increases in volume of distribution and total body clearance as well as decreases in oral absorption, area under the concentration time curve, peak and trough concentrations. All of these changes may result in decrease in drug exposure. Other than zidovudine, little is known about the pharmacokinetics of other antiretroviral agents during pregnancy. A number of studies have suggested a correlation between trough concentration: IC50 ratio and virological responses. The objective of the study is to examine the pharmacokinetics of antiretroviral agents during different stages of pregnancy in comparison with the non-pregnant state (post-partum and historical control). HIV infected pregnant women in general good health who are on at least three antiretroviral drug combination will be enrolled in the study. Pharmacokinetic profiles of the antiretroviral agents taken by the subjects will be obtained two to four times during pregnancy and again at around one month post-partum. These data will be used to assess the need for dosage adjustment or therapeutic drug monitoring of antiretroviral agents during pregnancy.