Each month, your body gets ready for pregnancy. The uterus grows a thicker lining to receive a fertilized egg, and an egg is released by the ovary in a process called ovulation. The reproductive cycle happens because of two hormones in the body, estrogen and progesterone. Their levels rise and fall over the course of each month.
NuvaRing contains synthetic versions of these hormones. When they’re introduced to your body, certain steps in the reproductive cycle change. Ovulation doesn’t happen, the texture of the uterine wall doesn’t change, and mucus in the cervix thickens to block sperm from getting through.