Why are THOSE out? (tmi)

So this is kind of embarrasing. Last weekend it was really nice out. While the two older boys were napping I was letting Jake play in the baby pool. I decided to take my shirt off and go topless to get some sun without tan lines (again sorry if tmi). Shouldn't have been a problem because even if someone drove down our driveway I would have plenty of time to put my shirt on before they saw me. So after the boys had been sleeping about 45 minutes (they usually sleep atleast 2 hours) Nate comes running out of the house, looks at me and says "Why are THOSE out?" and points at my chest! Augh!