Nexplanon is effective immediately if it is inserted within the first five days of the menstrual cycle. If inserted at any other time during the cycle, backup contraception is recommended for seven days to ensure full protection against pregnancy. This is because the implant releases etonogestrel, which prevents ovulation, thickens cervical mucus, and alters the uterine lining to prevent pregnancy. In summary:
- Inserted within days 1-5 of the menstrual cycle: Effective immediately.
- Inserted after day 5: Use backup contraception for 7 days.
This timing ensures maximum contraceptive effectiveness based on the menstrual cycle phase during insertion.
