well theoretically yes it is possible by the generally agreed 'rules' of omegaverses. but whether they both actually give birth would be up to chance and other biological factors like the individual's health, quality of the individual's reproductive cells etc etc.
in a more '"realistic"' sense though, both being pregnant at the same time would be very very rare, especially due to the fact that omega sperm have really low fertility rates and alphas in general are hard to get pregnant (which is partially why "purebred" alphas in a lot of omegaverse are deemed as very high class and like royalty.). after doing a quick google search (i.e. take this with a grain of salt instead of actual medical advice), it takes around 2-3 weeks after sex for pregnancy to occur and some people can notice symptoms during that first week. assuming the omega was pregnant first (because its the easiest), they would have to be very vigorously doing the deed for at least 2-3 weeks (not straight, just more often) because once you notice signs of pregnancy, the mother carrying the child has to be careful with their body or else they could run the risk of miscarriage and their own death.
if it ever happened that both were pregnant at the same time it would be as often as winning the lottery, but a sensible couple would not try to because then their partner can't help them when they're in pain and/or cannot do something themselves
Made a chart hahahaha
https://pic1.mangago.zone/r/post/19/md_1066950_e0d9728668a846f14363811f88caaf96.jpg
So apparently female alphas can just 'grow' one... imagine if the omega was a guy and the female was an alpha. Does that mean they can both get pregnant?