Influenza vaccination in the first trimester was not associated with an increase in major malformation rates and was associated with a decrease in the overall stillbirth rate. This information will aid in counseling women regarding the safety of influenza vaccination in the first trimester.

II.

Objective To determine pharmacokinetic parameters for oseltamivir in all trimesters of pregnancy. Methods Thirty pregnant women, 10 per trimester, receiving oseltamivir phosphate 75 mg were recruited to study first-dose pharmacokinetics. Plasma samples were obtained at 0, 0.5, 1, 2, 4, 8, and 12 hours after the first dose. Samples were analyzed for oseltamivir and oseltamivir carboxylate levels. Using a noncompartmental model, area-under-the-curve (AUC), maximum concentration (Cmax), time-to-maximum concentration (Tmax), and half-life (T1/2) were estimated. Results There were no significant differences in the pharmacokinetics of oseltamivir by trimester except for an increased T1/2 in the first trimester for oseltamivir phosphate and an increased Cmax in the third trimester for oseltamivir carboxylate. The levels of oseltamivir carboxylate observed were within the range needed to achieve IC50 concentrations for pandemic H1N1. Conclusion The pharmacokinetics of oseltamivir do not change significantly according to trimester of pregnancy.