Does it deserve to be rated so low? No, but I'm only giving it the worst rating possible to make up for all the undeserved high rating it got.
What really bothers me about 'My Girlfriend's Child' is that it's a guide first, story second.
I can't help but feel like the author wants this manga to be a guide for teenage girls on how to act if they got pregnant, which... is fine on paper, yes do write stories which young readers can use the MC as an example of what to be or not be, but it's SO on the nose in 'My Girlfriend's Child', it bothers me to no end.
Because this manga is so busy being a guide, (such as leaving notes telling readers that a pregnant woman shouldn't skip on food, cause you know you wouldn't want them to pick up the wrong idea on what to do or not if they got pregnant!) the story element takes a backseat, and it's a shame cause I find how each family handles the news of their children's mistake to be interesting, but it's hardly the focus.
And if I were to speak on the main couple for a second, I just have to mention the male lead. He's too perfect. Not that I think he should be abusive towards the female lead, nothing like that, but he's so perfect, he doesn't feel human. It's nice that he's such a kind person who always wants to put her first, but again, it goes into the territory of the author making the male lead a guide on how teen boys SHOULD behave if they found themselves in this situation.
I think what this manga lacks the most to me is the wonderful flaws REAL humans who find themselves in this situation have. If you want a guide on how to behave during teenage pregnancy and how to handle it, this manga is for you! If not, do not pick up for the story.