Your first child is about to stop being the only one.

She's been told a baby is coming and she said “okay” and went back to her puzzle, and you can't tell whether that means she's fine or she hasn't understood yet. Then last week she started asking to be carried again. She's three. Nobody has explained to her what she's about to lose, because nobody has words for it that don't sound like a warning.

What actually helps

• Don't sell it as a playmate. The baby will not play with her. For a year it will cry, sleep and take you away from her, and if you promised a friend she will conclude you lied. Say what's true: at first the baby will mostly eat and sleep and cry, and that gets boring, and later they'll play.
• Tell her what stays the same, in specifics. Same bed, same school, same person who does bath time, same story afterwards. Continuity is the thing she's actually asking about when she asks where the baby will sleep.
• Give her a real job, not a fake one. “Mummy's little helper” is a title. “You choose which sleepsuit” is a decision. Small real choices land; ceremonial ones don't.
• Let her be unimpressed. If she says she doesn't want the baby, that is information, not a discipline problem. “You're allowed to not want it. You can tell me that any time” keeps her talking to you.
• Expect the regression, and don't punish it. Baby talk, wanting a bottle, night waking, accidents after months dry. She is checking whether the small-child job is still available. It is.
• Protect one thing that is only hers. Twenty minutes, same time, no baby in the room. Short and reliable beats long and occasional.

Why a book helps here, when talking doesn't

Every conversation about the baby is a conversation you start and she endures. A book is one she can start, at the moment she wants it, and stop when she's done. She'll go back to the page that worries her most, again and again, which is how you find out which part she's stuck on without having to ask.

A book about her. The baby is a supporting character.

Her name, her room, the thing she's best at, the toy that is not up for negotiation. The baby arrives somewhere in the middle and she is still the person the story is about — which is the whole point, and the thing she needs to see in print.

Or the whole book in outline, for her to color.

You choose how it's drawn: painted and full color to read tonight, or the same story in plain outline for her to color herself.

The second one also gives her something to do with her hands during a month when a lot of the attention in the house is pointed elsewhere.