The five year expiration date is given by the manufacturer and I suppose has to do with the lifespan of the materials. THe manufacturer recommends using it from 37 weeks. If you will use it twice a day, then even if you go early you will benefit from the practice. If you are that early, then the baby will be small anyway and you probably won't tear. Also, from a hormonal view, the body is not ready for such stretching before. I doubt that there would be a problem if you used it from 36 weeks, but the manufacturer does recommend from 37 weeks.