Now the thing about having a baby — and I can't be the first person to have noticed this — is that thereafter you have it.

The humor comes from stating a life-altering fact in the flattest possible terms: once you have a baby, you don’t return to a prior, unencumbered state. Kerr’s mock-earnest aside (“I can’t be the first person to have noticed this”) highlights how new parents can feel as if they’ve uncovered a startling revelation that is, in reality, universal. Beneath the joke is a clear insight about permanence and responsibility: parenthood is not an event but an ongoing condition. The line’s durability lies in its compression of a complex emotional transition—joy, shock, loss of autonomy—into a single, deadpan sentence.