They had originally planned to get the kids married if it turned out that Chin-hwa was pregnant, but Woo-bin raised an objection, saying Chin-hwa was too young to be a mother.
Plus, he still had his whole life ahead of him, so would he give it up to get married and have a child?
Of course, getting married and having a child didn't mean one's life was over, but Woo-bin exaggerated it a lot.
He made it clear that Chin-hwa was young and his body wouldn't be able to handle it.
There was no way he would risk Hwa's life over a child he could get in the future.
Even if they took precautions, the plans for the marriage were still underway because Baek-Hyun strictly said that the choice was Chin-hwa's alone.
And it was what he decided that they would do. And he would not allow any influence to change Chin-hwa's mind, so Woo-bin should take a breather and stop antagonizing the situation.