NuvaRing is a so-called combination contraceptive. This means that it emits two hormones: progestin and a form of estrogen. These active hormones, which end up in users' blood stream, are the very hormones that mean the contraceptive is effective. They are also the cause of weight gain in a minority of NuvaRing users. NuvaRing itself lists weight gain as one of the possible side effects of this birth control method, in as many as three separate places. And even though a quick internet search will lead you to many reports of individual women confirming that weight gain can indeed be caused by NuvaRing, this does not mean that you will personally necessarily gain weight while using this contraceptive.
Less than five percent of NuvaRing users reports weight gain, which means than more than 95 percent do not gain weight on this form of birth control (that doesn't say they don't experience any of the other NuvaRing side effects, of course!). Don't let the potential prospect of weight gain deter you from trying out the NuvaRing as your chosen form of contraception. But, keep in mind that you can put on some extra pounds, and try moving to another contraceptive if this is happening to you. You may also like to explore one of the more surprising side effects of NuvaRing in our article about NuvaRing side effects for men.