Yes, in the end, the woman get pregnant with the MC.
There's only one ending (although there is a single choice in the game which allows her to film herself in front of an audience, and then she'll develop a fetish of being seen and penetrated by strangers in the park....).
After the end of the game, you unlock the after story where they all live under the same roof, the husband's daughter has grown up and become a teenager, the husband is sitting in front of the MC with the baby he had with the husband's wife, and the wife is on the side).
After this scene, they fuck again in another room, and that's the end of the story.
I'm not sure whether the husband has divorced her or whether they're all living together, but if I were in his shoes, I'd of course have filed for divorce, but I guess the couple are better off living on the husband's money and need him because their income isn't enough to live together.
The daughter seems to love her father, so the wife can't really abandon him.
What does the English version of the game say?
Having played the Japanese version with very little time to translate everything, there are some words and phrases I couldn't translate.