It's a tough question, but there are ways to minimize negative results. The more "common ground" you have together the better. The old saying "opposites attract" might have been true fifty years ago, not true today.

In a relationship, you need to be on the same page. Whether that page is filled with wedding rings and babies or condoms and cheap hotels, it doesn’t matter: A new study finds that unequal levels of commitment breed the most hostility in a relationship.

Even partners who were both uncommitted were less hostile in videotaped conversations than mismatched partnerships, the researchers found.

We can help. To see if she’s as committed (or not) as you, remember that relationship patterns don’t develop in a vacuum, explains lead study author Minda Oriña, Ph.D., professor at the University of Minnesota. “Our upbringings play an important role.” Ask these non-awkward questions to see if your girlfriend is likely to stay or stray. (Remember: These are all factors that just make a woman more likely to want commitment, but they won’t apply to every woman. To find out for sure, you need to ask!)

Did you feel comfortable talking to your parents as a kid?

The study also found those who had supportive families at age 2 and who comprised with their friends at age 16 were more likely to be the more committed partner in the relationship at age 20.

“A supportive family would make her more likely to want commitment out of her romantic relationships,” says Oriña. “She’s more likely to call upon you for help and make her needs known.” On the contrary, if she lacked a support system, she might be afraid of being hurt—and as a result—be less likely to commit.

via Men's Health: Will She Stay or Stray?.