I heard that vitamin C can make you have a miscarriage. Can it cause a miscarriage if the egg have not been fertilized yet or is being fertilized?

It's a myth. Some people are repeating the internet myth that vitamin c can cause a miscarriage. There are many internet myths, and sometimes it is hard to tell what is real and what is not. Don't worry about vitamin c, and it's fine to keep eating oranges, tangerines, and cuties... Unless you're trying to avoid sugars and carbs.