The Problem With Pronouns

A few months ago Spencer was questioning me about how babies get out of the mommy's stomach. He was no longer satisfied with my stock answer - at the hospital, so I (gingerly) gave him more detail about how babies are born. The other night (apparently after digesting this information for a period of 3 months or so) he asked me how babies could fit and actually get out of there. I told him that it stretches. He looked surprised, then asked, "so how long and skinny do the babies get?"