Alpha females can get pregnant. But its harder for them to be. It is why some bloodlines have pure Alpha families. A male alpha marries a alpha female and have alpha children.
Usually in many omegaverse stories though, in pure blood families, omegas are shunned or disowned...rarely are they seen as a bonus in an Alpha dominate family.
Well by logic standards...its omegaverse XD. None of it is really logical. Especially when so many authors do omegaverse but always switch around the rules.
The most common ones are
Omega
Beta
Alpha
And its yaoi so this almost always mostly aimed at men. But there have been a few series that have gone into very light details about females.
This includes Alpha females having a tendency to being less fertile than beta and of course Omega. Just because they are female doesnt change the fact they may have issues.
Even in some omegaverse an omega may have a harder chance of getting pregnant if he isnt at his most fertile point.
Wait, what do you mean alphas can't get pregnant? So alpha females are infertile?