Nexplanon is the most effective reversible contraceptive available, with fewer than 1 in 1,000 women becoming pregnant per year of use. In clinical trials, the implant had a first-year pregnancy rate of 0.27 per 100 women-years, and the FDA recently approved it for up to five years of use with zero pregnancies reported during years four and five.
How Effective Nexplanon Is by the Numbers
Across large clinical trials, Nexplanon’s three-year pregnancy rate (called the Pearl Index) was 0.38 pregnancies per 100 women-years of use. To put that in real terms: if 10,000 women used the implant for a year, roughly 27 would become pregnant during that first year. Over three full years, the number rises only slightly. That makes it more effective than every other reversible method, including both the copper and hormonal IUDs, which also fall into the “less than 1 pregnancy per 100 women” category but have slightly higher real-world failure rates.
For comparison, the birth control pill has a typical-use failure rate of about 7 pregnancies per 100 women per year. That’s because the pill depends on taking it at roughly the same time every day. Nexplanon has no user error once it’s in place, which is the main reason its real-world effectiveness matches its clinical trial effectiveness so closely.
Why Pregnancies Still Happen
When pregnancies do occur with the implant, the cause is almost never the device itself failing. A study of 200 contraceptive failures among over 20,000 Australian women found that 84 of those pregnancies were caused by improper insertion, meaning the rod stayed inside the applicator or fell out during the procedure and was never actually placed in the arm. Another 46 women in that study were already pregnant at the time of insertion without knowing it, and 19 failures resulted from the implant being placed at the wrong time in the menstrual cycle.
That breakdown is important because it shows the implant’s biggest vulnerability is the insertion process, not a decline in the hormone over time. If the rod is confirmed to be in your arm (you or your provider can feel it under the skin), genuine contraceptive failure is extraordinarily rare.
Medications That Reduce Effectiveness
Certain drugs speed up how quickly your liver breaks down the hormone in Nexplanon, which can lower the amount circulating in your body enough to allow ovulation. The most notable ones include some seizure medications (carbamazepine, phenytoin, oxcarbazepine, topiramate, felbamate), the antibiotic rifampin, the herbal supplement St. John’s wort, and certain HIV and hepatitis C treatments. If you take any of these, you’ll typically need a backup barrier method while on the medication and for 28 days after stopping it.
How the Implant Prevents Pregnancy
Nexplanon works through three mechanisms at once. Its primary action is suppressing ovulation, so no egg is released for sperm to fertilize. It also thickens cervical mucus, creating a barrier that makes it difficult for sperm to reach the uterus. And it changes the uterine lining in ways that make implantation less likely even if the first two defenses were bypassed. This layered approach is what gives it such a low failure rate.
Timing of Insertion Matters
If you get Nexplanon inserted during the first five days of your period (or during the placebo week of a combined pill pack), it starts working immediately. If it’s placed at any other point in your cycle, you need to use condoms or another barrier method for seven days while the hormone builds to effective levels. Getting the timing right at insertion eliminates one of the few windows where an unintended pregnancy could occur.
The Five-Year Approval
Nexplanon was originally approved for three years of use. The FDA has since extended that to five years based on data showing no pregnancies during years four and five, with a Pearl Index of 0.0 during that extended period. This means you don’t need to rush to get the implant replaced at the three-year mark, though your provider may still recommend checking in periodically. The hormone level does decline gradually over time, but clinical evidence shows it remains high enough to prevent pregnancy through year five.
Fertility After Removal
Unlike some long-acting methods that can take months to clear your system, Nexplanon’s effects reverse quickly. It’s possible to become pregnant within days of removal, and ovulation can return within the first cycle. If you’re having the implant removed and don’t want to conceive, you should have another contraceptive method ready to start the same day.