Oh, and my son is 8 months old now and doing fantastic
Yes it happened with my son! It is fairly common and almost always fixes itself before birth. In more severe cases it usually corrects itself by the age of 1. My doctor had me do an additional ultrasound un my 3rd trimester to see of it was corrected. Also of its only slightly dilated it Can be a result of the ultrasound angle. My doctor said if there's one thing to come back wrong in an ultrasound that is the one he would choose. Even if it didn't correct itself the only problem it should cause is potential urinary tract infections.
Did your doctor seem concerned?