They both involve shotgun marriage, and falling in love during the pregnancy process. Though the circumstances in both dramas are different, the main point is the same. They also pass through similar hardships.
It's a remake of the Taiwanese version. All three dramas (Fated to Love You - Taiwanese, Fated to Love You- Korean, and Dekichatta Kekkon), cover the same problems, dealing with baby before marriage and love along the way.