
This is an Omegaverse manga which means there are 3 type of people, Omega, Alpha and Beta. (Can read more about this genere of manga if u click the tag to know more about it)
Lets start with Beta,
Beta is normal humams with normal reproduction system but they are normally all normal class citizens
Alpha,
They are the most superior amongs the 3 groups, they are normally like company president or born in a very wealthy family. A female Alpha have a dick which can use to impregnat an Omega
Omegas,
They have the ability to become pregnant with an Alpha's baby, they go into a process called heat (i forgot how many time per month or once per 3 months) and during this time they will let out a smell which will attract the Alphas to gp wild and wanna have sex with the Omega in heat. During this time, the omega will easily become impregnated with a baby.
Another this is that a Alpha will mark an Omega by biting the back of the Omega neck like the bite mark we saw on masaki's neck. This way the Omega cannot have sex with anyone else besides the Alpha that has marked him.

This is called an omegaverse. Meaning there exists alpha's, beta's, and omega's. Since this is a "new" or "different" universe than what we see in the "real world", it is possible for male omega's to get pregnant. I don't know the biology behind why, but in an omegaverse, it happens. Far as I know, an omega male can only get pregnant with an alpha male. Could be completely wrong, but this is just based off the limited knowledge I have on this omegaverse. Also, you can see female-female pairings and pregnancy can occur through their partnership as well.
Hope that helps!

Thanks, that's help a lot. Because when he said he pregnant 10 months I mean what and how can? And he got sick(catch a cold and body heat), I'm dying in curious because it's the first time in the manga he said about alpha-omega.
The other day i read sex pistols but that's supernatural genre the male got pregnant. But it was normal because supernatural genre.

Well, since an omega male can have a uterus and a 'vagina' I would suspect that female alphas have a dick and boobs....

Um, it said right in the link, so I am confused as to why you asked the question, again...?

Yesh, they will react when they smell an Omega in heat and they would want to impregnate them and inorder to do that cause Omega guys have a reproductive system in their ass so in order to impregnate them they have to have a dick :) U should read some Omegaverse Manga cause some manga have the explanation in the first few pages! :3 Have fun reading! Its actually very interesting :3

No problem! Glad it helped :) As for his sickness, he caught a cold and went into heat at the same time. So that was why when they talked about the cold medicine not working well, Maa-chan said to Yuuki that he took the injection and he will be fine soon. The injection he took was the heat represent. Maa-chan being in heat was also the reason that Papa didn't bring Hikaru to him. Being an alpha, Maa-chans heat would have affected him too greatly. Hence sending Yukki, who would not be affected as easily.
Yeah they didn't say it was an omegaverse until later on. The author assumed people knew what the omegaverse was :)

Here, I looked for a link to help explain. It does not belong to me, I did not write it!
http://puppylover857.deviantart.com/journal/Omegaverse-Explanation-and-Guide-441250200
Hope it helps!

Just now I look on Google and began to understand a little, so I can say that male omega have 2 organ reproductions penis and vagina right?
Sorry it's new for me, because in school we just study male and female. Not alpha-omega
My fantasy make me accept male to male (yaoi) but not girl to girls.
My logic confused anatomy omega body .
Sorry for the inconvenience because not enough study.

No need to say sorry, got to start somewhere right? If you look at the link posted above, it explains the reproduction for both female-female, male-male, and male-female :) hope this clears things up a bit.
Hiro-san is alpha.
Masaki is omega.
What's the meaning alpha and omega.
Hiro-san(seme) & Masaki(uke) are a man, but Masaki got pregnant and gives birth to hikari.
I'm confused. How can a man got pregnant?