Well, I am not a parent, but every time they find out, they usually spazz out. I'm sorry if this is is not exactly the answer you wanted. But it is just because they don't want you to grow up. My dad usually reacts by joking around with me and telling me not to get pregnant, at which a slap his arm lightly. My mom usually reacts by hugging me and squealing and asking all kinds of questions about who he is, what he looks like... it pretty much sucks. If your in highschool, they realize it's going to happen. But if you are in middle school, they will give you a talk about not making stupid decisions with boys.
They say things like ooooh thats so cute, and I remember when I, and awe puppy love. Then they tease you about it for the rest of their lives. Or atleast mine did. If you are into someone, suggest you don't let on.
they usually worry and kinda hope it doesn't get to serious to where you wanna grow up fast or not need them anymore my parents worry that ill get serious to fast and start a life right away so there scared and worry but thats normal its best not to tell them until your getting serious with the person
As a dad, it was a non-issue for my wife and I. We raised our daughter in a loving, caring home. She was a good girl and we trusted her to make the right choices. She maintained her grades and obeyed our curfews. I met her boyfriends and didn't have any problems with any of them. She had a few secrets from me, but told her mother everything (I imagine). Today, my daughter is in her 30's and lives a healthy single woman's full life. She lives a few hours drive from us and has had the same full time job for over 12 years. Yes, you could say my wife and I are proud of her.