 This is a pilot study of the use of oseltamivir in pregnancy. This data will be combined with data from the parallel Pediatric Pharmacology Research Unit PPRU studies to put together a portfolio for use in understudied populations. This will allow for a re-thinking of the current status and potentially allow for small trials to be performed with patients who are suffering from influenza in pregnancy, to assess efficacy. The relevance with the pandemic strain and its corresponding Minimum Inhibitory Concentration MIC may have direct implications for dosing in pregnancy if lower levels of drug are documented. In addition, depending on the findings from the esterase component of the investigation, future investigation into mechanistic bases for changes in enzyme activity are possible. 