We'd first have to ensure that the vaginal flora doesn't undergo radical changes during labor. If not, it should be easy to do. The hardest and most expensive

We'd first have to ensure that the vaginal flora doesn't undergo radical changes during labor. If not, it should be easy to do. The hardest and most expensive part (for mice) would be a sterile C-section to prevent the mice from picking up the wrong bacteria. If it does, the mother's bacteria may have to be complemented according to the expected changes.