Travel outside US when OPT extension application is pending

I'm a planning a trip outside US during the time that is after submitting OPT extension, but before 1st year OPT ends (about 1 week before expiration date). Will I be getting trouble re-enter US when I come back? What are the risks? I've searched online and consulted from lawyer. The answers are pretty much "In theory, you can but we don't recommend" without pointing out the risks.