Responses
In the earlier chapters when Minshit and Haesoo was abt to do the deed, Haesoo asked Minshit to wear a condom and he just lost it. He got angry and said that they didn't need that and "as if ur getting pregnant" or something along the lines so I have a hunch that they did have a baby but lost it/miscarried the baby and that caused complications with Haesoo's body.
It can also be the reason why Haesoo was very eager to marry Minshit again and be a family. Maybe it's the why Haesoo was not that intimate with Minshit too
I bet you within future chapters she’s (Ari) gonna end up pregnant, Mincheol’s gonna spaz out on her, and somehow this news will get to the FL.
(May not be an accurate prediction so take this with a grain of salt)