anyone in omegaverse can give birth
Miyauchi himself comes from an alpha Dad (women) and beta Mom (women)
In the omega verse both sexes (female and male) and all sub-genders (alpha, beta, omega) can give birth.
Betas can have kids. It is just the Miyauchi, himself, was told that he most likely wouldn't be able to. Basically he was told by a doctor, when he was in his late teens or early adulthood, he was infertile. So he had been worried about that. But then he did manage to get pregnant after all.
Just like the comments above clarified all genders and sub genders can give birth, but the "fated pair" thing is something alphas and omegas have, while alphas have stronger sperm, omegas are extremely fertile, having the betas with a reaaaaaally low fertility rate, even worst for Miyauchi whom was told to be unfertile (luckly for him, he was not and got himself a baaaby). And so most stories focus on the "fated pair" themes and on alphas x omegas pairs, but with creativity, you can do whateeeeeever you want o/
im a bit confused, betas cant get pregnant right? so how did they have a baby did they adopt? or is a beta able to give birth in this manga?