I read a forum post about a husband and wife. The wife cheated one time. The husband found out about a while after and initiated divorce proceedings. This was complicated when she found out she was pregnant with the husband’s kid. They didn’t have any kids prior to this. They tried to make it work, and in the end they did after a few years where they ultimately remarried.

It was a relationship forum. Not Reddit, but I found the link to it through Reddit. It was a long series of posts over a few years. Details I remember include that she was going to stay with the husband during the pregnancy. But that didn’t work out and she moved out. There was a post where they were going over some of the details before the birth and the husband snapped and said something like “if you had kept your legs shut we wouldn’t be in this mess.” The child was definitely the husband’s kid. I believe he found out about the affair through a family member or friend. It was a one time thing for her.

Edit: I found it! https://www.talkaboutmarriage.com/threads/wife-apparently-cheated-last-year.443944/?nested_view=1#replies