By Lauren Mann of the National Campaign to Prevent Teen and Unplanned Pregnancy

This week's episode of "Teen Mom OG" saw two new additions to the cast: Both Maci and Kristina are expecting! And while we want to congratulate them on their pregnancies, it's also a great opportunity to talk about planning and preventing pregnancies if you're not ready to start (or expand) your family quite yet.

Kristina and Gary admit that they weren't trying to get pregnant, and you can see the shock on both of their faces when they find out they're expecting. They'll both step up and continue to be great parents for Leah and the new baby, but it also raises the question of what they were doing for birth control. For someone with his own personalized condom line, Gary may need a refresher on exactly how to use them.

Maci, meanwhile, had found out that it could be harder or impossible to get pregnant again -- so while she and Taylor weren't trying to conceive, they also weren't doing anything to prevent it. Remember: Every time you have unprotected sex, there's a chance of pregnancy.

If you're not actively doing anything to protect against pregnancy, it's basically the same as trying to get pregnant. And if you're using a method of birth control, you need to use it correctly, every single time you have sex. There are so many methods out there -- barrier methods like condoms and hormonal methods like the pill, the ring, the shot and the patch. Your safest bet? A long-acting, reversible contraception like the IUD or the implant, plus condoms to prevent against STIs, especially if you're not in a monogamous relationship or have multiple partners.

For more information about all the methods available, check out a great resource: Bedsider.org. And be sure to catch a brand-new episode of "TMOG" on Monday at 10/9c.