A wedding often takes months and months of planning. You have to choose the ring, scout Montgomery venues, taste various cake samples, and even figure out how to keep Aunt Martha far enough from your mother so that no fights break out. Unfortunately, planning a wedding also means making preparations in case it ends in divorce. Most people say "I do" without any protection in place, but with a little extra time and planning, you can have a prenuptial in place before the big day.
Raising a child is difficult enough, but not knowing if that child is yours is a serious concern to bare. Eventually, you may decide that you need a DNA test, even though you love your child. At that point, you'll either be proved to be the biological father or be told you aren't related to the child.