Objective: To describe the pharmacokinetics of tenofovir and emtricitabine in the third trimester of pregnant HIV-infected women and at postpartum. Design: A nonrandomized, open-label, multicentre phase IV study in HIV-infected pregnant women recruited from HIV treatment centres in Europe. Methods: HIV-infected pregnant women treated with the nucleotide/nucleoside analogue reverse transcriptase inhibitors (NRTIs) tenofovir disoproxil fumarate (TDF 300 mg; equivalent to 245 mg tenofovir disoproxil) and/or emtricitabine (FTC 200 mg) were included in the study. Twenty-four-hour pharmacokinetic curves were recorded in the third trimester (preferably week 33) and postpartum (preferably week 4-6). Collection of a cord blood sample and maternal sample at delivery was optional. Pharmacokinetic parameters were calculated using WinNonlin software version 5.3. Statistical analysis was conducted using SPSS version 16.0. Results: Thirty-four women were included in the analysis. Geometric mean ratios of third trimester vs. postpartum 90% confidence interval (CI)] were 0.77 (0.71-0.83) for TDF area under the curve (AUC(0-24 h)); 0.81 (0.68-0.96) for TDF C-max and 0.79 (0.70-0.90) for TDF C-24 h and 0.75 (0.68-0.82) for FTC AUC(0-24 h); and 0.87 (0.77-0.99) for FTC C-max and 0.77 (0.52-1.12) for FTC C-24 h. The viral load close to delivery was less than 200 copies/ml in all but one patient, the average gestational age at delivery was 38 weeks. All children were tested HIV-negative and no congenital abnormalities were reported. Conclusion: Although pharmacokinetic exposure of the NRTIs TDF and FTC during pregnancy is approximately 25% lower, this was not associated with virological failure in this study and did not result in mother-to-child transmission. (C) 2013 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins AIDS 2013, 27:739-748