How does the Imperium keep its population numbers?
New 40k enjoyer here, trying to learn some lore. The more I learn about the Imperium, the less I see how can it keep so many population with how bad the life at the hive cities is and a state of constant war all over the place. For a human civilization to keep its population equal it needs around 2.1 kids per women, but idk how they manage to get to that point with millions of astra militarum dying weekly (plus all the other jobs that are a fancy death sentence), and I don't think life expectancy is that high in the Imperium. Is there any reason I'm missing out or is the Imperium really fucked in the long run?
Edit: Holy shi I'm getting slimed here