This is the never-ending mom mystery! My best friend and I have the same problem and are baffled by it. My mom insists that it's moths, but we don't have moths and it's only my clothes. I figure it can't be the washing machine because we wash mixed loads - my kids', husband's, and my clothes all together. I have 22 month old girl/boy twins, and this happened when my daughter was little, too. So it's not some freaky twin thing. But I don't remember having the holes later - like when my older daughter was 3-4 and before my twins were born. They were NEVER in my maternity shirts. I have no answer for you, but I'm still experiencing the same phenomenon! My only solution has been to buy cheap shirts or wear sweaters because I hate ruining the more pricier ones and the sweaters don't have the same problem. I'm both glad and surprised to know that there are many other moms with the same mysterious problem, though I still wonder what's going on!!!