It's a thing in the omegaverse genre. Both, a rut and heat intensify pheromones. However, a rut is way more intense than a heat, so the intensified pheromones can cause an omega to suddenly go into heat as well. That's at least how I understood it through reading several omegaverse stories and from the wiki.
but think of the same way that it works in animals there is no need for a heat if the animal is already pregnant because the goal of reproduction is already achieved only in very rare cases does a heat and pregnancy occur at the same time. a lot of times heat is related to a period in normal humans so the math not mathing
The cycle in the omega verse may be related to that of animals and derived but it's still fictional. Anything is possible in the fictional world. For some stories of the same genre, pregnancy does (not) matter. In this case, it doesn't. Pregnant male omegas work the same as any other female being in real life. Pheromones do not influence the pregnancy, only the instinccts of their second gender.
how'd he get his heat (unless it was metaphorical) while pergnat???