The idea of girls impregnating each other in a fictional universe is quite out of the ordinary. Fictional worlds often build on real-world biological principles or create their own logical systems, but this particular concept is not a common one. It could potentially exist in a very imaginative or alternate reality-based story, but it would need a lot of creative explanation to make it seem plausible within that fictional framework.
It's very rare to find such a concept in fictional settings. Usually, reproduction involves specific biological processes that don't permit girls to impregnate each other. This kind of idea might be explored in very unconventional or fantasy-driven stories, but even then, it would likely come with its own unique set of rules and explanations.
In most fictional universes, such a concept is highly unconventional and unlikely. Biology and reproduction typically follow certain natural laws that don't allow for this.