Contraceptive implants are a long-term birth control option for women. A contraceptive implant is a flexible plastic rod about the size of a matchstick that is placed under the skin of the upper arm.It releases a low, steady dose of a progestational hormone to thicken cervical mucus and thin the lining of the uterus (endometrium). Contraceptive implants typically suppress ovulation as well.One version of contraceptive implant - Implanon - was recently discontinued by its manufacturer and replaced with a newer version called Nexplanon. Nexplanon is radio opaque, which means it can be seen on X-ray, which is useful for checking the location of the implant. Nexplanon is the only contraceptive implant with Food and Drug Administration approval available in the U.S.