"Where babies come from" for an adopted child

In the New Haven Review, an account of talking about birth, babies and adoption:

There’s a baby in Emily Brownlow’s tummy. Emily Brownlow babysits for my daughter Saskia most Friday mornings so we’ve been watching her belly rise like dough in a bowl and talking about the baby inside.

The timing’s good for us—to see this belly rise, and mull that whole “where babies come from” question. Saskia turns three in about a month, around the time Emily Brownlow’s baby will be born. The timing’s good for us not because Saskia’s going to have a baby brother or sister—we are not, Saskia’s the fourth, our eldest is fifteen and we are done with babies—but because Saskia is adopted and Emily Brownlow’s belly provides an opportunity to talk about birth and babies—and adoption.

What do you think?