The subjects enrolled in this study will take an antiretroviral based regimen containing raltegravir twice daily both during and after their pregnancy. The specific regimen will be chosen by their own primary care provider based on their antiretroviral history and resistance testing. They will undergo a series of blood sampling for pharmacokinetic analysis over 12 hours on two occasions; a) during their 3rd trimester and b) approximately 3 months postpartum. Concentrations of raltegravir in the infant will be assessed by cord and infant blood sample at delivery and a blood sample at approximately 3 months of age.