I think it really all depends on the author. Some authors create an omegaverse where all genders can get pregnant, but omegas are just the most likely because of their heat cycles.
The omegaverses where only omegas can get pregnant would, in my opinion, definitely have a population decrease...but hey, population control? ╮( ̄▽ ̄)╭
As far as I understand in omegaverse anyone can get pregnant. That's why in a lot of tragic omegaverse story, arranged marriage is done between alpha to preserve the line. For example in one omegaverse story, alpha (the seme) is paired up with beta (the uke) and turns out the beta has difficulties getting pregnant. He told him, that when it comes to it, he will consider getting pregnant instead if the beta truly wants a baby.
alpha or beta, they can get pregnant. That's why the seme said he will be the one getting pregnant next cause he couldn't stand seeing his partner doing it alone lol
The story is great, there's just one major plot hole. They're both male ALPHAS, so how is it even possible for them to have a baby? Only females and male omegas actually have a womb. ╮( ̄▽ ̄)╭