In this study, we are looking at blood concentrations of Kaletra in HIV positive patients during pregnancy. The patients will come in for 4 visits lasting ~24hrs. These visits take place at 20-24 weeks, 30 weeks, 32 weeks and 8 weeks post-partum. At the end of vist 2 (week 30), we will increase your dose to 2 adult Kaletra tablets, and one pediatric Kaletra tablet (total dose 500/125mg). The dose will remain increased until you are 2 weeks post partum, then it will return to the standard 2 adult tablets (400/100mg).

Inclusion Criteria:

• HIV positive
• Pregnant (<22 weeks)
• Currently taking or planning to start Kaletra
• ≥18 years of age

Exclusion Criteria:

• Active opportunistic or serious bacterial infection at the time of entry
• Past or present obstetrical complications (including, but not limited to: placentia previa, eclampsia, confirmed birth defects, multiple gestation pregnancies)
• Unable to maintain medication adherence, defined as ≥ 80% of doses taken between visits
• Currently receiving or expected to receive other protease inhibitors in conjunction with Kaletra®
• HIV genotype showing accumulation of protease inhibitor mutations expected to result in virologic failure on Kaletra® OR documented virologic failure on Kaletra®-containing regimen attributable to the Kaletra® component
• Chronic hepatitis B and/or C virus infection
• Cushing's Syndrome
• Untreated hypothyroidism or hyperthyroidism
• Serum Creatinine > 1.5 mg/dL
• Amylase 1.5 times ULN and/or abnormal lipase
• Direct or total bilirubin levels > Grade 1
• ALT/AST > Grade 2 (based on the NIH Division of AIDS (DAIDS) Table for Grading the Severity of Adverse Events
• Bicarbonate > Grade 2 (DAIDS)
• Hematology > Grade 2 (DAIDS), except for anemia: exclude only women with Hb< 9 g/dL and/or HCT , 27.3% (< 8.5 mg/dL and/or HCT , 25.6% if currently on ZDV) at screening; all subjects with anemia who enroll in the study must be receiving or start hematinics, including iron and folate supplements, immediately upon enrollment and continue until anemia resolves or end of pregnancy. The hematinic supplements may be discontinued at the discretion of the investigator if they consider continuation would not be in the best interest of the subject.
• Receiving the following drugs: astemizole, terfenadine, rifampin, cisapride, ergot derivatives, simvastatin, lovastatin, St. John's wort, pimozide, midazolam, triazolam, carbamezapine, phenobarbital, phenytoin, or dexamethasone