Nexplanon is a highly effective, long-acting reversible contraceptive consisting of a small, flexible rod inserted beneath the skin of the upper arm. It offers continuous protection against pregnancy for up to three years. The most commonly reported side effect is a change in the user’s typical menstrual bleeding pattern, which is often the primary concern for individuals starting this contraception.
How Nexplanon Changes the Menstrual Cycle
The implant works by continuously releasing a low dose of the synthetic hormone etonogestrel, a type of progestin. This steady hormonal input prevents the ovaries from releasing an egg by suppressing ovulation. It also causes the cervical mucus to thicken, creating a barrier that makes it difficult for sperm to travel.
Etonogestrel also directly impacts the endometrium, the lining of the uterus. Normally, this lining thickens cyclically and sheds if pregnancy does not occur. The hormone from Nexplanon causes the uterine lining to thin and stabilize instead.
Because the lining does not build up cyclically, the regular, predictable shedding known as a true period does not happen. Instead, the altered hormonal environment leads to sporadic and unpredictable bleeding as the thin lining sheds intermittently.
Expected Bleeding Patterns in the First Three Months
The initial 12 weeks following Nexplanon insertion are characterized by high variability as the body adjusts to the continuous hormonal release. The implant immediately affects the uterine lining, meaning there is no predictable date for the first bleed. Many users experience frequent, light bleeding, often referred to as spotting, which is the most common pattern during this adjustment period.
Spotting can occur at unpredictable times and may last longer than a typical menstrual period. In some cases, bleeding may be heavier than expected, or cycles may start heavy and stop abruptly. The pattern observed during these first three months is often broadly predictive of the individual’s long-term pattern.
Some individuals may experience a rapid cessation of bleeding almost immediately after insertion. This wide range of experiences, from constant spotting to no bleeding, is considered normal as the body adapts to the steady dose of etonogestrel. This initial irregularity is the most frequent reason for concern during the first few months of use.
Long-Term Cycle Outcomes and Variability
After the initial adjustment period, which typically lasts three to six months, the bleeding pattern tends to stabilize, though it remains highly individual. For many users, the long-term pattern involves a significant reduction in bleeding or a complete absence of it. Up to one-third of users eventually experience amenorrhea, the complete cessation of menstrual bleeding.
Other individuals settle into a pattern of infrequent or light bleeding, which may manifest as light spotting only a few times per year. However, a minority of users may continue to experience frequent or prolonged spotting and bleeding even after the adjustment phase.
This persistent, unfavorable bleeding pattern is the most common reason why users choose to have the implant removed early, affecting approximately one in ten women.
When to Consult a Healthcare Provider
While changes to the bleeding pattern are expected with Nexplanon, certain symptoms warrant immediate consultation with a healthcare professional to rule out other medical issues. Heavy and prolonged bleeding that feels excessive or disruptive should be evaluated, particularly if it involves soaking through pads or tampons hourly for several consecutive hours. This type of severe bleeding could indicate a need for medical management.
Any signs of infection at the implant insertion site must be addressed promptly, including severe swelling, spreading redness, warmth, or the presence of pus. Suspected pregnancy should also be investigated if bleeding suddenly stops or if other pregnancy symptoms arise. Additionally, severe, debilitating pelvic or abdominal pain requires medical assessment.