Omegaverse

In Omegaverse lore, I understand how male omegas work: they usually still have male anatomy, but they can get pregnant. What confuses me is how female alphas and female omegas work anatomically in stories where same-secondary-gender pairings can have children.

For example, in a female alpha/female omega relationship:
- Which one gets pregnant?
- Does the female alpha have some kind of reproductive anatomy different from a typical female body?
- Is the female alpha able to impregnate someone biologically, and if so, how is that usually explained in Omegaverse settings?
- Or is the female omega the one with altered anatomy instead?

I’m basically asking what the common anatomy and reproduction rules are in Omegaverse fiction for female alpha/female omega pairings, female alpha/ male beta pairings, because I mostly only see explanations for male omegas.